Proton 5.13 requires Steam Linux Runtime - Soldier.
Its a different Steam Runtime to the one referred to in STEAM_RUNTIME=0 so this is not an issue.
Hello @StarterX4, this is intentional and expected. Steam Linux Runtime - Soldier is a container environment in addition to being a separate and updated set of runtime libraries. Proton 5.13 is built on top of the Soldier runtime instead of the older Scout runtime, and LD_* style runtime setup which STEAM_RUNTIME=0 influences.
proton 5.13x3 2020-10
When the STEAM_RUNTIME=0 environment variable is set, running any game with Proton 5.13 forces installation of "Steam Linux Runtime - Soldier". Uninstalling it and trying to run the game keeps installing it again.
I don't want a bunch of deprecated useless libraries taking up 500MB of my disk space.