> I can connect to my P2S in LAN mode with OrcaSlicer just fine (currently using the latest 2.4.0 nightly).

You either haven't updated the firmware or you also enabled "Developer mode" which has its own issues.

> This is a separate issue, I think even Bambu Studio can't connect to printers in LAN mode on a different subnet.

It's not a separate issue, it's a long-standing bug in their proprietary networking plugin that they refuse to fix. Orca slicer has implemented a hacky workaround so it actually works there.