8Bitdo Ultimate Bluetooth. I use it with the included dongle and it works just fine on my distro (Nobara). Kubuntu should also be fine I guess, just make sure you're on a recent kernel (6.3+)

The main reason why I'd recommend this over others is that it has built-in macros - which is really handy for some games where you may need to press a complicated button sequence (like in fighting games), and of course, it also has the classic "turbo" feature which is handy for platformers.

The other reason is that the controller also works great with the Nintendo Switch as well as Android, so if you ever decide to game on these platforms you can reuse the same controller.

Edit: I just remembered that when I first got mine, I needed to update the firmware to get it to work correctly. You'll need to update the firmware on both the receiver (v1.03) and the controller (v1.05). You'll need to do this one at a time (update the receiver first, disconnect it, then connect the controller directly via USB and update it). Unfortunately the firmware updater tool works only in Windows or macOS, so that's one drawback I guess. But maybe in the future it could get updated via LVFS/fwupd.