[rwmj]

x.com isn't even accessible from Firefox. It tries to trick you into turning off enhanced tracking protection claiming it is "known to cause issues" (the "issues" presumably being with them invading your privacy).

[delichon]

I just accessed x.com from Firefox 143.0.1, and there was no such message or claim. It just displayed the site without any warning or ceremony. I have not visited the site with this browser before.

[SoftTalker]

In my experience, it's often blocked if it's embedded in another page. You can visit x.com directly without issues.

[rwmj]

You probably have enhanced tracking protection turned off. The message appears for me right now (FF 143.0).