Don't know if this will help. But I had 500 errors too. I think I'm on the right track now.
Tried PHP 8.0 and 8.1 still same problem like you.
I went into the database and set the language and default locale to en_US.
MAKE SURE YOU HAVE A FULL BACKUP!!
/os_config/default_locale = en_US
/os_config/system_language = en_US
