Copying and pasting some of this from the 36 roster hack thread:
I managed to get this to run on my Linux desktop without much hassle. For reference, I am using Proton-7.0-3 for this game. I just installed OCP and the roster hack as expected. However, before installing the roster hack, one of the files needs to be renamed so it gets loaded properly. In the unzipped roster hack, enter the ui folder then under the models folder, rename "m_team_stage.IGB" to "m_team_stage.igb" without the quotes.
For this game to launch with the roster hack, make sure that "WINEDLLOVERRIDES="dinput8=n,b" PROTON_NO_ESYNC=1 PROTON_NO_FSYNC=1 %command%" is present in the launch options for this game under Steam, without the outer quotes. WINEDLLOVERRIDES is necessary for Proton to properly use the dinput8.dll file. It's unrelated to the mod, but disabling ESYNC and FSYNC prevents the opening videos, menu, etc. from running at 1fps even on an unmodded install.
I also tried to get OpenHeroSelect to work, but to no success. That's probably going to need to run on Windows.