Xbox Series S & X UI, anything known?

Probably yes, because so far we saw that the UI from the series X is the same than the Xbox One, S and X. So yes, you should be able to play with friends on Xbox Series X.

Hi Jaden,

This is one of the known issues on the Series X|S consoles

Known issue: Some users are experiencing issues launching Xbox 360 games, which instead return the user back to the Home screen on Xbox Series X|S consoles.

Workaround: Clear your Xbox 360 storage by going to Settings > System > Storage > Clear local Xbox 360 storage.

Hope this helps!

Xbox One UI is continuously going through enhancements and I believe it would be a similar UI for the series X with no major changes.

Hello CapitanYT,

Thank you for your post. I understand you have some questions on the compatibility of Rockband and Guitar Hero controllers with the Xbox Series X/S. Currently there is no information regarding the compatibility of these controllers, it is only known that
the Xbox Series X/S will support controllers that are usable with the Xbox One.

I hope this information helps.

The leak in question was an error on the part of Microsoft...they incorrectly listed is as X/S in a blog Post about an Update to the UI:

"This article has been updated to feature a new hero image, as the original mock up incorrectly listed an Xbox Series X|S Optimized version of “Batman: Arkham Knight.” “Batman: Arkham Knight” is available for players on Xbox Series X|S only via backwards compatibility."

https://news.xbox.com/en-us/2021/03/10/discover-games-on-xbox-in-your-preferred-language/