Twitter is fully X.com now.

"All core systems are now at X.com", so why opening x.com links in private window redirects to https://twitter.com/x/migrate?tok=, then again to x.com? I just cannot describe how stupid this is.

As others have noticed, it drops an error: "Firefox’s Enhanced Tracking Protection (Strict Mode) is known to cause issues on x.com". The link has ?mx=2 parameter. I removed it and the page loaded correctly (but half of the viewport was clumped with banners). I tried again in a new private window, but never saw this error again, so this is a bug due to the aforementioned redirect.