Is it ok to use Special K HDR Retrofit (HDR Retrofit | Special K - The Official Wiki) with Last Epoch ?
It is way better than auto HDR windows provide. I does not hurt my eyes 
Special K is not recommended to be used while playing a multiplayer game as the game may take issues with Special K or its injection service!
Newer versions of Special K and its frontend SKIF automatically manages the injection service and by default stops it on a successful injection as well as when the frontend app (SKIF) is closed. This means that the user just needs to ensure that the Special K Injection Frontend (SKIF) app is not running in the background when the user is starting a multiplayer game.