How do you play poe2 on Linux?

Through steam. Valve has made it simple enough that you just click install and then click play like in windows. There could potentially be additional steps depending on the game but proton which was developed by valve acts as a translator, allowing Windows game applications to function properly on Linux systems. games get patched regularly by proton which sometimes also includes additional performance increases or bug fixes windows does not have. It's a pretty cool tool.