tl;dr In a recent thread on Mastodon, it was revealed that Ubuntu 23.04 users can’t install the Steam deb package from the Ubuntu archive without jumping through some technical hoops. It turns out this was a mistake, a bug was filed, and future builds shouldn’t have this problem.
Steam - the game store/launcher from Valve requires a bunch of 32-bit libraries to function. Many of the games that Steam installs also require many of these various libraries. These older games are likely never going to get updated to have 64-bit clean builds.
The thread on Mastodon brought up an expected thought process, though. The conspiracy theory-minded might (reasonably) think “This is Canonical breaking the deb, so you’re forced to use the snap”. But that doesn’t appear to be the case.
It’s just a simple mistake that is fixed, and now (a selected set of) i386 packages will be easily accessible again.
TL;DR is that wine doesn’t yet support WoW64 (Windows on Windows64), which enables the running of 32-bit binaries on a 64-bit system - it’s conceptually similar to multilib on Linux. You can’t run 32-bit Windows bins on a purely 64-bit WINE as I understand it.
But the Steam launcher doesn’t run on Wine. Some games may run on Proton but one shouldn’t depend on the other AFAIK?
well, Wine does support WoW64, but the way it’s implemented requires you to install both 32 and 64 bit Wine.