I got myself a lovely streamdeck XL and had some issues getting it to work with streamdeck_ui on Linux Mint 20. It turned out that the usual howtos don’t include the Device id required for the XL model which is 008f, so simply add the following line to your udev rules:

SUBSYSTEM=="usb", ATTRS{idVendor}=="0fd9", ATTRS{idProduct}=="008f", TAG+="uaccess"

reload the udev rules as per howto, replug the device, now streamdeck_ui should have no issues attaching to the HID device when running as a normal user without root permissions.

Unplugging & replugging