Okay, first time trying, I play on Windows, and I play on a Druid (to level 5). Back on Linux, the character is lost, but this time I have to log-in, so I figured I didn’t log in before.
So I log in. I have my Rogue which becomes a Bladedancer, and after 11 hours of playing I get to mapping. Great. Because of some performance issues (lag at low quality) on Linux, I figured I’d try to play on Windows. No problem at maxed out quality.
Then I go back to Linux, and I figured I’d try to use Proton Experimental to see if that would fix the performance problems. After that, I lost my level 55 something character, and thus 11 hours of progress.