Hi @twa
Yes, you can untar locally and then FTP. You’ll still need to “install” the plugin if you do it that way, though since some plugins also have schemas that need to be created in the database.
Do you have shell access? OJS comes with a command line tool specifically for this purpose:
php lib/pkp/tools/installPluginVersion.php plugins/generic/yourPlugin/version.xml
Where you’d replace the path to version.xml with the correct one for your plugin. If you don’t have access yourself, perhaps your systems admin can do this for you.
Best
Jason