Your system information

• Steam client version (build number or date): 1766529085
• Distribution (e.g. Ubuntu): SteamOS
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs: steam-logs.tar.gz
• GPU: AMD

Please describe your issue in as much detail as possible:

I play ULTRAKILL on my Steam Deck, primarily docked (JSAUX hub) and using Desktop mode because I need music, and I use keyboard + mouse to play FPS. Whether I play modded or vanilla does not matter, in both cases when the game is closed, Steam never catches onto that and assumes I'm still playing ULTRAKILL. This led to me amassing a few fake playtime hours on the game, because I go take a break, close the game, and then come back to see that the game is still "running". The only way to stop it from doing that is to press the "Stop" button in the Steam UI. This did not happen on my regular PC. Best way I can describe this in a nutshell is that "ULTRAKILL never counts as closed by Steam when closed".

Steps for reproducing this issue:

1. Open ULTRAKILL in Desktop mode
2. Close in any way you want to (alt+f4, quit from main menu, etc)
3. Look in Steam for ULTRAKILL
4. Find it still running

Notes

This occured to me on Steam Deck, specifically the Galileo model. I have my FS set to RW mode permanently since I want to use my SD as a normal mini PC, and need to use pacman.
I apologize in advance if I'm incoherent.