


Works perfectly out of the box
The only issue I had is the game having no WM_CLASS, so if you use GNOME the game will have no icon and name in the dash.
V1.08 added language support and some easter eggs from the console versions, but broke input latency in a way that always causes an input delay.
You can install this mod https://gamebanana.com/mods/512850https://gamebanana.com/mods/512850 into the game's directory in Desktop mode to fix the input delay and make it much more enjoyable in my opinion. Just don't use this fix if you intend on submitting any speedruns.

Works perfectly
Works well, no tinkering needed

There is just one tiny moment when you're asked to use the keyboard quickly, which is complexe with the recommended configuration, but not detrimental at all.
Very good native. No issues.

Native support and works right out of the box.
Undertale works right out of the box because it has native support. In a worse scenario, you can run the Windows version with Proton or Wine, but I haven't dealt with that issue.
The window is tiny by default. There's some key combination to make it fullscreen. Same on Windows, though.
Worked out of the box. Great game also.

The game runs even better than on windows, even for some tinkering about reseting about some special runs, like Genocide route.
Made all the possible runs using the native version, and it's just perfect ! For doing a true reset, you just have to remove the UNDERTALE directory from your .config directory, not having to search everywhere like on windows.
Now works natively

Game's native on Linux so....!
Perfect in performance and feel. Nothing to say.

Always freezes at the same point
I only was able to start the game with Proton 7.0-6

gamemoderun gamescope -w 640 -h 480 -W 1920 -H 1080 -S integer -F pixel -- %command%
Gamemode+Gamescope added to force integer scaling. Gamescope alone caused input lag.
PERFECTION
Perfection. Not a single issue.

Play Undertale with Windows version: choose Proton version 4.2-9. Beyond this version, the game will not launch
Native works great out of the box. No problems
The game works perfectly out of the box but you have to change the control layout to move diagonally.
Simple controls, good handling, text is never too small to read.
Works just as you'd expect it to, it's perfectly fine
Had a bug with my DWM status bar, but I just had to hide it and unhide it again and it would be fullscreen.
Native version works without any tinkering
Runs perfectly without any issues natively.
I switched to the Windows version through Proton because my controller was not getting detected on the native port.
Native version does not start and does not show any error.
Native Linux game, runs perfectly OOTB.
This is a native Linux game, should run with zero issues on any distro.
F4 for fullscreen enables pixel perfect scaling
steam://controllerconfig/391540/2837960003
I really wanted to use a more Steam Deck optimized layout, so I created one.
Worked flawlessly
Worked like a charm. A truly beautiful experience