Given the steamrt3c link, my first guess would be that the experimental steamrt3c Steam Client might be running Proton games' setup commands (such as installing the Visual C++ Runtime) inside the steamrt3c container, ins...
Looks like the error message "The following component(s) are required to run this program: Microsoft Visual C++ Runtime" is related to SteamRT3. After disabling SteamRT3, the game is able to install the required componen...