

Mod Manager dev is intentionally preventing Steam Deck support so there's no real point to buy the game for Steam Deck.
No issues, works like native
Works like Native
Runs Smooth as butter no issues on proton 9 and ge. 9.5

Behaves exactly like it doies on Windows with one downside for people who want a better Super Monkey Ball experience.
Runs with no sweat playing the game at max settings at 800p. The only downside is that the Banana Mod Laumcher doesn't really work so no accurate controls or any other QOL mods or mods to make it more like the original like Dynamic Rolling Sounds, Timer Countdown Sound, Collision Fixes, Disabling Helper Prompt, Graphical Tweaks, and UI Enhancements.
You can replace textures and sound files to again make it a little more accurate to the originals and more presentable in terms of being a remake. Dole Bananas, Original Monkey Voices, Original Announcer, and restoring your regions DreamCast logo for the Sega Console DLC.
Runs fine vanilla, but the game doesn't see the mod loader on Deck which is a huge bummer.

Runs fine on a ChimeraOS Steam Machine
Build a machine utilizing ChimeraOS to act as a Steam Machine for the living room, and this plays flawlessly there!

Set the left thumbstick to use a square deadzone.
Plays great without any tinkering.
Added low sensitivity gyro controls, awesome experience.

As of this past Saturday (2022-03-22), I had to use Proton Experimental or the game would not register any input from either my keyboard/mouse or Xbox 360 Controller. Otherwise it works perfectly with them both on experimental.
Occasional stuttering - turning off vsync fixes
Game worked perfectly out of the box (after turning off vSync), xbox one controller picked up right away.
Turning off vSync fixed the graphical issues.
Runs just as well as on Windows.
Good performance and controller support
I played with a 360, PS5, and Switch controller. All worked. Runs fine. Leaderboards work. I didn't notice any issues.

Runs just fine, but DualShock 4 inputs didn't register
Game didn't accept DualShock 4 input

Game runs perfectly right out of the box
Switch Pro Controller's gyro doesn't work properly
Runs out of the box
Works flawlessly straight out of the box. No graphical issues, no performance issues - worked perfectly with an Xbox controller.
Tried to run it after install and nothing happens
Ran like native
played for a bit with proton experimental and the game ran like it was native
Game is very stable and runs out of the box using Proton Experimental

Used Proton -6.18-GE-1