Linux controller setup (udev rules)

SDL3 is the only input layer this app uses, on every platform, including Linux. On Linux, its raw-HID backend needs permission to the hidraw and usb device nodes to talk to a controller directly. Without that permission, a controller from one of the vendors below may fall back to SDL3's standard gamepad mode (buttons and axes only) or may not be usable at all, as the per-controller notes in support-matrix.md describe. Xbox pads are the one exception: they work through SDL3's standard mode without needing these rules at all.

.deb (automatic)

The .deb package installs the rules for you (post-install) and reloads udev. Just replug the controller after installing. Nothing else to do.

AppImage / manual install

The AppImage can't run an installer step, so install the rules once by hand:

sudo cp 99-relic-controllers.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules
sudo udevadm trigger

The rules file ships in the repo at scripts/build/linux/99-relic-controllers.rules (or copy it from the app resources). Then unplug/replug the controller (Bluetooth: re-pair) so the new permissions apply.

What the rules grant

TAG+="uaccess" gives the logged-in desktop user read/write access (via systemd-logind) to controllers from these vendors, over both hidraw and usb:

Vendor	VID	Examples
Nintendo	057e	Switch Pro, Pro Controller 2, NSO GameCube, Joy-Con
Sony	054c	DualShock 4, DualSense
Microsoft	045e	Xbox (usually XInput; included for completeness)
8BitDo	2dc8	8BitDo pads

If your controller has a different vendor ID, add a matching pair of lines and reload (udevadm control --reload-rules && udevadm trigger).

Xbox controllers work without the rules through SDL3's standard gamepad mode; the rules matter for the vendors SDL3 reads over raw hidraw/usb instead (Nintendo, Sony, 8BitDo).