Hello, I cannot use a Steam Cloud backup between my Windows 10 and ArchLinux session. Under Steam Windows, I can see my characters, they sync well with Steam Cloud but I can’t see them under ArchLinux (the Steam Cloud option is active under ArchLinux) and if I create a character under ArchLinux, it deletes the first character from my Steam Cloud backup under Windows. I lost a lvl 65 character some time ago and I don’t want to do the test again 
Thank you for the report.
I am very sorry, however we do only officially support Ubuntu. As a result of this, we are unable to guarantee that Last Epoch will work as intended on other distributions such as Arch.