When installing mods on Linux, the asset folders in the OMSI directory are CASE SENSITIVE. If new vehicles aren't showing up in the menu, or modded maps are loading to a blank void, check you don't have any duplicate asset folders with differently cased letters. For example: "Sceneryobjects" is the correct directory for map objects, but a mod might install a second folder e.g. "SceneryObjects", which the game will not look in. In such instances, you'll need to merge that folder's contents with the correctly cased folder. This isn't a problem on Windows, since the NTFS filesystem doesn't normally treat directories as case sensitive.

I've tried running Map Tools, which is a community debugging tool for OMSI which loads up a map, detects missing assets and helps you figure out why it's not loading properly. Both with and without protontricks, the program hangs and won't work.

I've found the game runs smoother, and with far fewer crashes than on Windows - thus far, no crashes at all, likely thanks to DXVK. Still no change to the huge lagspikes when loading new parts of the map, but that's an issue with the game itself.