Multiplayer and co-op

Patch 3.0’s notes are the best public list of what was breaking in co-op. They mention desync on a new co-op campaign, desync caused by a player’s notes, a failure to load after live-game was disabled, a crash on Xbox while joining a session in progress, and a duplicated save configuration the first time a PS5 joined.

Mods

The modding FAQ says every player needs the same main mods and the same sub-mods. Update 2.0 added a mismatch popup. Update 3.0 checks sub-mods as well and names the mods that differ. A friend on a newer Commuter Pier file is enough to split the session.

Platforms

Saves can be uploaded to a cross-progression slot, and the console patch notes talk about each platform’s save wording. I do not have a matrix that says PC can join a PS5 lobby. Until that matrix exists, this page only claims that each platform can play its own multiplayer.