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.
Depends whether you’re relying on the algorithm (recommendations) to find new groups or whether you’re manually searching for and vetting these groups yourself. If it’s the latter then it’s not luck, that’s a safe and smart approach to take with social media.