Firefox’s Enhanced Tracking Protection (Strict Mode) is known to cause issues on x.com
There were no “issues”; everything was working completely fine. This is a deliberate decision to force people to turn off tracking protection.
I saw a recommendation to use Firefox’s container extension https://support.mozilla.org/en-US/kb/containers, but it’s disabled in private browsing windows, and I always use private browsing windows.
The project was using a way to bypass requiring a backing account to proxy the requests, but the API update broke that
The instances that chose (and choose) to go the extra mile by creating and maintaining proxy account(s) are the ones still working
If the instance gets too popular the twitter goons quickly figure out what the proxy account is and ban it, though. So it’s a constant game of cat and mouse.