For the time being I'm installing Windows 10 and setting it up without ever logging into a Microsoft account. (There's a trick during first-time setup where if you disconnect your internet, it lets you create a local-only account.) I haven't actually tried Windows 11, but I hear it makes this significantly harder or maybe impossible, which is definitely making me wary.
People at LAN parties actually do log into their own Steam accounts, but logging the whole machine into a guest's Microsoft account feels worse. Then again, I haven't tried it, maybe it'll turn out convenient, if it lets people sync their settings between machines? Note that at the end of the party, all changes anyone made to any machine are wiped out.
That said it's definitely comforting to have Linux as another option if Microsoft makes Windows unusable for this use case!
If you have a Pro license and you specify you intend to domain join the PC, Windows 11 drops you out to a local account, but there's no escape for Home licenses. It's pretty much impossible to remove that from Windows unless they decide to let you domain join from the OOBE, but that would be too convenient for sysadmins so it'll never happen.
Do you run your own Steam content caching server, or do weekly Steam Backups to have local kinda-recent images of the bigger games (or do you just download it fresh post-wipes)?
I maintain a primary disk image with all the games installed. During a party, all the machines boot from that same image, except each with a private copy-on-write overlay. Any changes made on a machine are written only to the overlay. At the end of the party I delete the overlays. The primary image remains in exactly the state it was in before the party.
So before each party I just have to install updates on one computer, like a normal person would. No need for a special cache. (Or arguably, the primary image is the "cache".)
Gotcha, so if there was a big update during a party you'd have to either let everyone update themselves; or delete their overlays, download the update to the primary, and then make new CoW overlays for everyone.
I'm not sure about op, but I actually run Lancache (lancache.net) locally on our network. It supports Steam, Windows Updates, Epic games, and pretty much anything else served over http.. (https://github.com/uklans/cache-domains).
This is all assuming you're not using a domain etc.. and have any of the myriad of other tools setup. We run lancache strictly for the fun-net segmented network.