Valve recently announced the Steam Deck, their version of a Nintendo Switch that's actually just a portable PC. Steam Deck will run a custom Linux-based operating system designed by Valve, but with the help of Valve's Proton translation layer, normal Steam games will run on Deck. What's more is that both Games Pass and Xbox's cloud streaming service will work on Steam Deck, too.
While it was assumed Games Pass and Xbox's cloud streaming service for games would naturally work on Deck, because the device can run Windows and take advantage of those services like any other Windows user, Head of Xbox Phil Spencer recently confirmed on Twitter that Games Pass and xCloud were on Steam Deck and working well.
Though, we don't yet have official word on how exactly Games Pass or xCloud works on Steam Deck. It's possible Spencer installed Windows on his Steam Deck, him working at Microsoft and all, and used those services on Windows on Steam Deck.
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It's also possible Microsoft has a Steam Deck version of Games Pass or xCloud that would come to Steam and could be downloaded and installed on Steam Deck's custom Linux-based OS itself.
Microsoft has shown itself to be very interested in bringing Games Pass and xCloud to as many platforms as possible. Games Pass only makes money if there are enough monthly subscribers that bring the company in enough profit to pay for the licensing deals to get and keep games on Games Pass. So, these services coming to Steam Deck makes a lot of sense.
Exactly how well Games Pass or xCloud works on Steam Deck remains to be seen, but it's reasonable to expect that if the device takes off, Microsoft will take steps to actively support it. Though, if the Steam Deck ends up as popular as the Steam Link, then active support becomes a lot less likely.