A mention in this week's Steam Deck firmware patch notes has some observers speculating that Valve is preparing to release its well-regarded Linux build for third-party hardware....
Since you're talking about ownership, remember that most "purchases" via Steam have DRM in them. If you really want to own your library then purchase from GoG and have your games downloaded to an external harddrive. You can easily access your GoG library via Heroic on Linux.
That's up to the game developers, not Steam. Many games on Steam don't have any DRM, you can copy the files anywhere you want and just start the exe without Steam even being installed.
I bought Minecraft on pc, downloaded an apk, logged in with my Microsoft account, and I can play on online servers. Seems like it can be shared, but Microsoft doesn't want you to.
Mknecraft pocket edition doesnt even need the microsoft account you connect it to to have minecraft installed
The only protection minecraft bedrock has against privacy is if it cant detect if the game was bought from the play store(at least on android, i dont know about java)
You can also find a pirated version of minecraft on the play store (the exact same game, works even in multiplayer, the only difference is that it comes with a texture pack that you can remove)