RandomStranger

I’m not sure I follow the question. I’ll try to list the steps.

1. Install distro
2. Install steam
3. Mount NTFS drive
4. Add steam library in NTFS drive (point to existing Window library)
5. Let steam recognize the game and install potentially missing files
6. Create EXT4 partition disk (preferably done already when installing distro)
7. If EXT4 game partition is not main drive, mount it and create steam library on it
8. Move game files.

Hopefully that makes sense. Somewhere along the way steam will probably install Proton as well. It might work straight from NTFS too, maybe? But I didn’t get it to on Linux Mint

Just to add, since I recently started to switch. Steam will find the game if I mount the “old” NTFS drive and point my steam library to it. It will be able to download missing files and appears to launch the game. The game doesn’t start though. After adding a EXT4 partition, I was able to add a library there and use the “move installation folder” in game settings. Then it works.