OP said their son in his friends use Xbox Series X/S, so that effectively removes Krunker and Minecraft Java Edition. That said, I believe Minecraft Bedrock Edition is available for XSX.
Stardew Valley is great, but the son’s social group has 5 people. Stardew Valley only supports up to 4.
Cities Skylines does not have multiplayer.
Can’t speak for Dorfromantik, because I haven’t played it, but the rest seem like great choices.
You should! The beginning may be a bit slow, but before long you’ll be building sweet bases or exploring the underground or doing whatever you like, really. It also has a ridiculous amount of content with even more to come next year, apparently. Also, no hunger/thirst mechanics! Like yourself, I don’t like 'em. Terraria has HP and MP, that’s it.
As a Switch owner, fuck this. This is reason enough for me to stop buying games on the Switch and go full piracy/emulation mode. I don’t have any Denuvo games on my PC and I am not having any on my Switch.
Oh, my poor, poor wallet. I loved C:S and this just looks better in every way. Well, except Linux support, but hopefully Steam Play will be able to mitigate that.