The windows version works mostly fine on linux (tested on Archlinux with Wine 5.11) however the game hangs when switching the audio output to another sink in pulseaudio.
I just tested the Linux build, it seems to work quite well, however there is some lag, especially in the first level for some reason. I had graphics on medium and I still dropped quite a few frames.
Other than that, it's fun and intuitive, and the levels feel very atmospheric.
There might have been lag on the windows build but for most types I wouldn't notice because I ran it with a Ryzen 3700X and a RTX 2070 SUPER. I will try the Linux version when I get to it.
The first level and the credits both lag and I'm guessing it's because those are the only levels where the portal preview recurses indefinitely. An easy fix would be to just cut off the recursion after 1 or 2 iterations.