As reported previously, Capcom recently updated MONSTER HUNTER RISE with new Enigma DRM and the update ended up breaking it on Steam Deck / Linux Desktop. But it should no longer be an issue no matter the Proton version used.
Valve did already work around it, updating Proton Hotfix to enable the game to run again, and Valve has even set Proton Hotfix as the default for now. So even if Capcom didn't patch it, the game was still playable again thanks to quick work from the Proton developers.
Now though, Capcom has updated the game directly and the updated recent patch notes on Steam have an addition at the top to now note:
We have released a patch that addresses the issue of the game not running on Steam Deck after installing update Ver.22.214.171.124.
We apologize for any inconvenience this may have caused.
Testing it myself today it does run just fine once again with Proton 8 and Proton Experimental without issues. ICYMI: Proton 8.0-5 was also just released!
It's good to see Capcom actively work to fix up their mess, but it's a shame this happened in the first place. Perhaps in future they will be more careful to not break their Steam Deck Verified rated games. Clearly Capcom don't see the Steam Deck as an important enough platform yet if they're not testing updates before pushing them out.