Doing so defies the Flatpak security model since the app needs raw evdev and uinput device access. Since Bazzite has a read-only root, you'll need to layer the runtime dependencies:

rpm-ostree install SDL3 SDL3_ttf  

Then reboot. The udev rule for uinput access goes in /etc which is writable on Bazzite:

sudo cp gamepad-osk.udev /etc/udev/rules.d/80-gamepad-osk.rules  
sudo udevadm control --reload-rules  

After that you can build inside a distrobox and run it from ~/.local/bin. I think these will work to build the current branch, I'm not on Bazzite (Fedora):

distrobox create --name build --image fedora:41  
distrobox enter build  
sudo dnf install golang SDL3-devel SDL3_ttf-devel libX11-devel wayland-devel  
git clone -b sdl3-migration https://github.com/0x90shell/gamepad-osk.git  
cd gamepad-osk  
go build -o gamepad-osk .  
cp gamepad-osk ~/.local/bin/  
exit  

Promptfont is optional (shows controller button icons on keys), but I recommend it. To install:

wget https://github.com/Shinmera/promptfont/raw/main/promptfont.ttf  
mkdir -p ~/.local/share/fonts  
cp promptfont.ttf ~/.local/share/fonts/  
fc-cache  

Nope. Just on my Arch systems (XFCE w/ X11) & Void Linux w/ X11. I am planning to run through some manual tests in KDE Plasma which should be applicable to Steam Deck and CatchyOS, but I need to build a proper test env. Ive done simple tests in Sway and KDE with nested sessions, but those are just spot checks not full testing. I need to boot into real systems for full testing.

Yeah, if it only handles the display side and relies on an accessibility framework like AT-SPI or IBus for input injection. That's how Onboard and GNOME's built-in keyboard work. But those frameworks need a cooperative desktop environment and don't work consistently across compositors.

This tool needs raw device access because it does more than just display a keyboard:

• Reads gamepad input directly from evdev (d-pad, sticks, buttons, triggers). Accessibility frameworks don't handle gamepad input, only keyboard/mouse.
• Injects keyboard and mouse events via uinput. AT-SPI/IBus can inject keystrokes but not mouse movement or arbitrary key combos like Ctrl+Z.
• Grabs the gamepad exclusively while visible so input doesn't bleed to the game. No framework exposes device grabbing.
• Emulates a mouse cursor from analog stick input. Continuous analog-to-mouse translation isn't something accessibility buses are built for.

TL;DR
Raw evdev/uinput is what lets it work standalone on any compositor without depending on desktop-specific APIs. The trade-off is device permissions instead of accessibility bus access.

No worries about the downvote. evdev and uinput are kernel interfaces, they work the same on Wayland and X11. The display side has native Wayland support via wlr-layer-shell (Sway, Hyprland, KDE Plasma). Steam does the same thing I'm doing for gamepad input - reads /dev/input/event* directly via SDL, creates virtual devices via uinput for remapping. Same kernel interfaces, same udev rules.

I pushed the Wayland branch to main and have an updated bin if you wanted to avoid building yourself, though you still need to follow my non-distrobox instructions to test.

SDL3/Wayland branch merged to main, bins updated along with AUR packages. Works fine in KDE with some caveats (opacity doesn't work and I can't teleport your mouse cursor - these are Wayland limitations/security).