Currently able to start the game and get into menus but cannot enter a stage. It doesn't crash, but politely tells me in-game that an error occurred and asks if I want to retry. Tailing the Proton log file, when I click 'yes', I get the same error in-game, and the log file tells me:
761596.292:0008:0009:trace:module:LdrGetDllHandle L"kernel32.dll" -> 0x7b420000 (load path L"Z:\\ssd\\Steam\\steamapps\\common\\OrcsMustDieUnchained\\Dashboard\\Bin;C:\\Program Files (x86)\\Steam;C:\\windows\\system32;C:\\windows\\system;C:\\windows;.;C:\\windows\\system32;C:\\windows;C:\\windows\\system32\\wbem")
Gist of one attempt's PROTON_LOG: https://gist.github.com/37b89da112e13c7dc29b02cb55892a87 (I attempted to click 'yes' several times, so there's a few of the above line clustered together with different timestamps to show where the error was happening.)
System specs: https://gist.github.com/3e575156101a239e0e786f0af5bdf223
It sounded like a different issue, but I did try to winetricks in vcrun2017 from the OP's comment, but the error was the same.
OMD:U has an intermittent issue where it crashes on start, present on Windows, that's fixed by installing VISUAL C++ 2017 (As per the last comment on this thread.
What looks like the same issue is happening on linux machine, hazy on the details there.