Possible lines of interest from the log:
err:wineusd:wineusd_initialize Failed to open target process, status: c0000022.
wine: failed to map the shared user data: c0000022
Confirmed working now on 5.0-7 (although now I am on Pop!_OS 20.04, and not Ubuntu 18.04)
proton 4.11-13x1 2020-04proton 5.0-6x1 2020-04
Compatibility Report
System Information
https://gist.github.com/julianlam/5bf221176d6ad8c509e6daf675a8caff
I confirm:
steam-352700.log
Symptoms
Game does not boot up on Proton 5.0-6, but works fine on Proton 4.11-13