Hi! I tried to update my site (joomla/k2) and got it on a new server with recent php versions. Now, I can see the homepage and item pages, but no so for "category" pages.

I get this error:
Fatal error: Cannot declare class K2ModelItemlist, because the name is already in use in /home/--site--/public_html/components/com_k2/models/itemlist.php on line 0

I don't know what exactly already has been using K2ModelItemList, I suppose some 3rd party K2 extension.

How do I know which extensions to disable to troubleshoot this? Or in other words, how do I quickly just see K2 extensions?

Thank you!