[mbwgh]

I am simplifying in saying that they outright block FF, but the site is broken with Enhanced Tracking Protection enabled [0], and has been for a while. They even mention FF in a dedicated error message, which I have to admit just grinds my gears :)

0 - https://cybernews.com/news/x-twitter-not-working-on-firefox/

[k_sze]

That's odd. I use X on FF with not only Enhanced Tracking Protection, but also a whole bunch of other privacy extensions (uBlock Origin, Ghosterly, Disconnect.me, DuckDuckGo Privacy Essentials, EFF Privacy Badger) without adding any exception for x.com, and it still works for me.

[0dayz]

Are you logged in to your account? Since I suspect that's why.

[tpm]

I just tried to enable ETP (had it disabled previously) on x.com and it works, so they must have fixed it.