Can I delete the folder /old_site after migration?

[CatfishPKR]

I have successfully migrated 20+ sites to Joomla 4.48.
With some of the sites (all on one specific shared hosting plan), I am having the problem that I cannot set the PHP version to 8.3 in my hosting cPanel - in Joomla, it still shows 8.0. I asked the hosting company's support and they tried to force PHP 8.3, with the result that the sites crashed when they did it, So we reverted back to 8.0.

When I go to Extension/Discover, I see a number of leftovers of old plugins that were installed from the Joomla 3.x installations long ago. There are a number of files related to those plugins in the old_site folder. I suspect they might be causing this?

Can I just remove that old_site folder or will it affect the site installation?

[AMurray]

you should have uninstalled those extensions before migrating....

Joomla 4 won't run (reliably) on PHP 8.3. Probably 8.2 or 8.1 is the maximum - but that also depends on extensions running on that version.

Perhaps now try upgrading to 5.x, as 4.x is shortly to end support (Oct 2024) except for critical security updates.
See https://developer.joomla.org/roadmap.html#R44 for the approximate Roadmap development/support schedule.

[CatfishPKR]

I followed the migration instructions to the letter, and I did deinstall all of those extensions, long ago. Before migrating, I deinstalled every plugin that was not coming from "Joomla Project", except translations.

I did try to migrate to 5.x, hoping this would fix the problem, but that migration failed - probably because of those remnants of old plugins. So, can you answer the main question: can I safely delete the /old_site folder or not?

[Webdongle]

No, not until you have your site working correctly. Best use a backup on wamp https://wampserver.aviatechno.net/ to perform an update/migration. Once you have it working use https://extensions.joomla.org/extension/akeeba-backup/