This release contains game-specific patches to get it to run and get saving working. Credit goes to GloriousEggroll for Proton GE and the brilliant people in this thread for coming up with the patches required to get this came running: ValveSoftware/Proton#3201
Installation works like any other version of Proton: Extract .tar.gz and put contents in ~/.steam/root/compatibilitytools.d
(or equivalent for your distribution, also compatibilitytools.d might have be to manually be created if you haven't used a custom Proton version prior).