Is Adobe XD done?

@Wim5F94 is correct. Luckily your learning will not all go to waste. Figma is quite similar (essentially the same kind of app just made by a different company), so you'll already understand quite a lot about it. There is more you can do with Figma, but what you've already learned will still help you. Best wishes.

You are not mistaken: the development team was disbanded last year, development stopped, and an Adobe spokesperson confirmed via a Bloomberg news article that they do not plan on continuing development. Adobe management had hoped to acquire Figma, but that deal fell through.

Adobe XD is indeed 'done' and over with, and you are best advised to stop learning and using it.

Teach yourself the industry standard instead: for better or for worse, that means Figma.

PS also this. It is made very clear that they will "determine the right time to end support for XD".