Does this also fix the random disconnections problem? (Or has that already been fixed?) That plagued me when my friends and I were playing through it last year.
Through proton, yes. The game has always worked with anti-cheat disabled (so no PvP multiplayer), but proton-compatible anti-cheat has been supported since early April, so all multiplayer functionality has worked since then.
This article is referring to a recent MCC patch that broke proton anti-cheat for about a week, thankfully it's fixed now.