No problems at all, it just works

Defaulted to 720p rather than 800p, easy enough to change in game.
Showed a mouse cursor in menus but not in game, even when not using mouse/touch navigation.

Works as others have stated with custom launch options: PROTON_USE_WINED3D11=1 PROTON_NO_ESYNC=1 PROTON_NO_FSYNC=1 %command%
PROTON_USE_WINED3D11=1 PROTON_NO_ESYNC=1 PROTON_NO_FSYNC=1 %command%
needs tinker to lauch, or else no window found.
Works out of the box
Click play, get spelunked, repeat
It run just as I remember it did on Windows, played perfectly on the Steam Deck docked or not docked.
Usei o comando de Gamemode só pra garantir, mas fora isso o jogo está rodando lindamente neste notebook out of the box com fps de 58 - 60.
gamemoderun %command%
rodou bem.
works out of the box
PROTON_USE_WINED3D11=1 PROTON_NO_ESYNC=1 PROTON_NO_FSYNC=1 %command%
Until i added PROTON_USE_WINED3D11=1 into the launch options the game would spew out a "Error getting monitor info" error and would proceed to crash.
works exelent!
The game was unable to get my monitor information
Unplayable
it just works

the intro stuttered a bit, but no other issues

Strange controller issue
With two controllers, P1 and P3 were simultaneously controlled by the first, P2 and P4 by the second
Mouse pointer showed up on first loading the game and couldn't get rid of it but went when actually started playing
Feels like an additional frame or two of input latency compared to Windows, but otherwise fine.
Changing the run toggle in the keyboard binding menu will disable the Steam Deck controller. Restart the game to fix this.
Runs smoothly with no issues at all, just like you'd expect.

6.21-GE-2 GloriousEggroll
Works great with no customization required
Steam controller integration (PS4 controllers) worked perfectly for both single player and local co-op.
Works perfectly

Other than a very minor work around for controller support, game runs perfectly.
Controller unresponsive unless started in BPM with controller recognition forced off.
Works flawlessly without extra setup
I initially had this game installed to an NTFS drive and it wouldn't launch. After setting the proper mount options, it launched. This is an update to my prior submission. This is using the latest Steam, Steam Play, and Spelunky versions available.

Crashed on startup, any Steam Play version
This is using the latest update from October

It just w o r k s
Buy the game it's fun

Game works fine as long as you aren't a speedrunner, if you are one then lack of bomb cascading is a big issue.
Bomb cascading does not work, making speedrunning with Proton a big disadvantage
Works fine
No problems encountered
Proton 5.13-6
It runs with no tweaking required. I recommend multiplayer with friends over remote play!
I had some controller detection issues but that happen on Windows as well with this game.