X.org doesn’t use that character. But e.g. TeX probably did before Unicode.

But X windows is dead or dying. Oh, so is Twitter?

I expect that 𝕏11 will survive twitter.

edit: using proper typography.

Reports of X11's death have been greatly exaggerated as far as I can see; it's still clinging stubbornly on, and efforts to kill it have tended not to go well.

Wayland is still trying really hard.

I hope not. I’m still using 𝕏Compose.