You should be able to add it to your steam library as a non-steam game and then in game options in Steam set up using Proton as long as you have Proton enabled for all games, not just verified games.
Heroic supports Epic, GoG, and now Amazon games. Supports installs, updates, file validation, and uninstalls perfectly. I think for Epic it supports cloud saves as well, but I don't use that feature and have heard horror stories from early adopters of it.