I'm currently doing some pre-checks and planning for an upcoming upgrade from Joomla 5 to Joomla 6, following the official upgrade guide (https://docs.joomla.org/Joomla_5.4.x_to_6.x_Planning_and_Upgrade_Step_by_Step).

My server environment is fully ready with the correct PHP and database versions. Everything seems fine, but when I try to disable the backward compatibility plugin as part of my testing, the frontend of the site crashes completely with the following error:

Class "JUri" not found

For this site, I am using the Edulif template. It seems like the template is still using the old JUri class instead of updating to the new namespace (Joomla\CMS\Uri\Uri).

Has anyone encountered this issue with the Edulif template before? What is the best way to trace down which file or override is triggering this?

Any guidance or tips would be super appreciated. Thanks in advance for your help! 🙏