This is a known issue with the Steam Client not Proton
[#5644](https://github.com/ValveSoftware/steam-for-linux/issues/5644)
Interesting. I've never had this problem until now.
Closing as a duplicate of https://github.com/ValveSoftware/steam-for-linux/issues/5644.
Every time I restart steam, ALL my Proton titles will show as an update available. Running the update seems to do nothing as well:
