OMP 3.4.0-8 trouble with locale of same language in different script (Serbian latin and cyrillic)

Hi,
My colleague and me are having problem with localization of our OMP installation in Serbian language in cyrillic and latin script.
We have installed latest OMP version with us adding translation po files for Serbian lat and cyr manually in installation files.
We do get Serban in Language toggle as Srpski and Српски as intended, but in admin and submission side there is no differentiation between two - it is either Srpski/Srpski or Српски/Српски, which leads to confusion which is which.

While installing we did get some warnings:

Deprecated: Smarty_Internal_Method_GetTemplateVars::getTemplateVars(): Implicitly marking parameter $_ptr as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_method_gettemplatevars.php on line 34

Deprecated: Smarty_Internal_Method_GetTemplateVars::_getVariable(): Implicitly marking parameter $_ptr as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_method_gettemplatevars.php on line 87

Deprecated: Carbon\Traits\Date::getDaysFromStartOfWeek(): Implicitly marking parameter $weekStartsAt as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/Traits/Date.php on line 1394

Deprecated: Carbon\Traits\Date::setDaysFromStartOfWeek(): Implicitly marking parameter $weekStartsAt as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/Traits/Date.php on line 1412

Deprecated: Carbon\Traits\Date::utcOffset(): Implicitly marking parameter $minuteOffset as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/Traits/Date.php on line 1481

Deprecated: Carbon\Traits\Localization::locale(): Implicitly marking parameter $locale as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/Traits/Localization.php on line 447

Deprecated: Symfony\Contracts\Translation\TranslatorInterface::trans(): Implicitly marking parameter $domain as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/symfony/translation-contracts/TranslatorInterface.php on line 62

Deprecated: Symfony\Contracts\Translation\TranslatorInterface::trans(): Implicitly marking parameter $locale as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/symfony/translation-contracts/TranslatorInterface.php on line 62

Deprecated: Carbon\Traits\Test::setDefaultTimezone(): Implicitly marking parameter $date as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/Traits/Test.php on line 203

Deprecated: Return type of Carbon\Traits\Date::createFromTimestamp($timestamp, $tz = null) should either be compatible with DateTime::createFromTimestamp(int|float $timestamp): static, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/Traits/Timestamp.php on line 29

Deprecated: Carbon\CarbonTimeZone::toOffsetName(): Implicitly marking parameter $date as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/CarbonTimeZone.php on line 158

Deprecated: Carbon\CarbonTimeZone::toOffsetTimeZone(): Implicitly marking parameter $date as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/CarbonTimeZone.php on line 172

Deprecated: Carbon\CarbonTimeZone::toRegionName(): Implicitly marking parameter $date as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/CarbonTimeZone.php on line 188

Deprecated: Carbon\CarbonTimeZone::toRegionTimeZone(): Implicitly marking parameter $date as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/nesbot/carbon/src/Carbon/CarbonTimeZone.php on line 230

Deprecated: Stringy\Stringy::__construct(): Implicitly marking parameter $encoding as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 77

Deprecated: Stringy\Stringy::between(): Implicitly marking parameter $offset as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 601

Deprecated: Stringy\Stringy::create(): Implicitly marking parameter $encoding as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 957

Deprecated: Stringy\Stringy::extractText(): Implicitly marking parameter $length as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 1324

Deprecated: Stringy\Stringy::lineWrap(): Implicitly marking parameter $delimiter as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 2652

Deprecated: Stringy\Stringy::lineWrapAfterWord(): Implicitly marking parameter $delimiter as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 2691

Deprecated: Stringy\Stringy::slice(): Implicitly marking parameter $end as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 3825

Deprecated: Stringy\Stringy::split(): Implicitly marking parameter $limit as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 3966

Deprecated: Stringy\Stringy::splitCollection(): Implicitly marking parameter $limit as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4007

Deprecated: Stringy\Stringy::substr(): Implicitly marking parameter $length as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4188

Deprecated: Stringy\Stringy::substring(): Implicitly marking parameter $length as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4216

Deprecated: Stringy\Stringy::titleize(): Implicitly marking parameter $ignore as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4364

Deprecated: Stringy\Stringy::titleize(): Implicitly marking parameter $word_define_chars as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4364

Deprecated: Stringy\Stringy::titleize(): Implicitly marking parameter $language as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4364

Deprecated: Stringy\Stringy::trim(): Implicitly marking parameter $chars as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4670

Deprecated: Stringy\Stringy::trimLeft(): Implicitly marking parameter $chars as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4694

Deprecated: Stringy\Stringy::trimRight(): Implicitly marking parameter $chars as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 4718

Deprecated: Stringy\Stringy::words(): Implicitly marking parameter $remove_short_values as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 5013

Deprecated: Stringy\Stringy::wordsCollection(): Implicitly marking parameter $remove_short_values as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/voku/stringy/src/Stringy.php on line 5063

Warning: Cannot modify header information - headers already sent by (output started at /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_method_gettemplatevars.php:34) in /home/blupressff/public_html/test01/lib/pkp/classes/template/PKPTemplateManager.php on line 1359

Warning: Cannot modify header information - headers already sent by (output started at /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_method_gettemplatevars.php:34) in /home/blupressff/public_html/test01/lib/pkp/classes/template/PKPTemplateManager.php on line 1360

Deprecated: Smarty_Internal_TemplateCompilerBase::compileTemplate(): Implicitly marking parameter $parent_compiler as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatecompilerbase.php on line 386

Deprecated: Smarty_Internal_TemplateCompilerBase::compileTemplateSource(): Implicitly marking parameter $parent_compiler as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_templatecompilerbase.php on line 417

Deprecated: Smarty_Internal_Runtime_CodeFrame::create(): Implicitly marking parameter $compiler as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_runtime_codeframe.php on line 28

Deprecated: Smarty_Internal_Runtime_Inheritance::process(): Implicitly marking parameter $parent as nullable is deprecated, the explicit nullable type must be used instead in /home/blupressff/public_html/test01/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_internal_runtime_inheritance.php on line 168

Can anybody help us to understand where the problem is, and how to get differentiation of cyr and lat script in submission?

Thanks in advance!