I am currently unsure whether SideFX wants us to submit bug reports for the XPU Alpha.
I would consider most features to be missing and not a bug. And I would assume that they are already aware of that. But there are occasions (like UVs getting screwed up on XPU) where I'm pretty sure that those are bugs.

Was there some communication on how this should be treated? Or maybe only Houdini FX customers are supposed to report on this Alpha, as it is with the Beta program?

Obviously, I am not counting on XPU as a render engine I can use in actual production but there are many situations I could benefit from it (or render parts of my scene) when issues like the buggy UVs would be fixed. Because overall, most of what is properly supported does work very stable and incredibly fast on my machine.

Did somebody already submit bug reports for XPU or know what SideFXs policy is on it?

I think it's a fair game to submit bugs to whatever you consider a bug

If they are aware of it they'll just merge the duplicate tickets

Yes please submit bugs when you find them (ie stuff which seems broken, rather than missing )

thanks!