Some lines of interest from the log: err:quartz:GetClassMediaFile Media class not found fixme:quartz:MPEGSplitter_query_accept {00000000-0000-0000-0000-000000000000}
I'm not using Proton but Wine-Staging with some additional patches from Tk-Glitch so this might be not apply to you, but it's worth checking if disabling the Large Address Aware patch actually fixes the problem.
I have the same hanging issue in the The Bard's Tale when the LAA patch is applied and enabled though the WINE_LARGE_ADDRESS_AWARE environment variable.
Maybe setting PROTON_FORCE_LARGE_ADDRESS_AWARE=0 or something equivalent would help in Proton.
Hello @mogorva, PROTON_FORCE_LARGE_ADDRESS_AWARE is not active unless explicitly requested or set in the Proton whitelist (as forcelgadd), and is not the case here because the log reads Options: set() in the header which tells us no PROTON_* settings were enabled.
Hi @kisak-valve, Ah, OK, I'm not familiar with reading Proton logs. Looks like we have a different problem. Sorry for the noise then...
Here is an update. Videos at intro and first ingame intro works with this Glorious Egroll release due to some Quartz improvements.
https://github.com/GloriousEggroll/proton-ge-custom/releases/tag/5.8-GE-2-MF
But game does hang at loading screen after you're done with ingame intro.
Progress: With Proton Experimental hangs does not occur. Game is playable,except video cutscenes and intro logos does not work. Video cut scene sections has this now. ( I know it is normal at this phase )

proton experimentalx1 2021-06PROTON_FORCE_LARGE_ADDRESS_AWAREx1 2019-10PROTON_FORCE_LARGE_ADDRESS_AWARE=0x1 2019-10WINE_LARGE_ADDRESS_AWAREx1 2019-10
Compatibility Report
System Information
I confirm:
Proton log:
steam-41900.log
Symptoms
Game normally does have a Linux version but unplayable due to input related problems. Windows version on Proton hangs at main screen.
Reproduction