Here is a simple tutorial on how to fix the Linux Startup crash.
How to Fix Linux Startup Crash
Larian Studios made an unnecessary new bloatware ♥♥♥♥ launcher for the game and in the process broke the game on Linux.
To fix it, open a terminal, cd to the installation directory:
cd ~/.local/share/Steam/steamapps/common/Divinity\ Original\ Sin\ 2/
Then run the following commands:
mv ./bin ./bin.bak
ln -s DefEd/bin bin
cd bin
mv ./SupportTool.exe ./SupportTool.bak
ln -s EoCApp.exe SupportTool.exe
Thanks to Ordon for posting this information (originating from protondb)
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