For anyone looking for the official suyu project it moved to this gitlab https://gitlab.com/suyu-emu/suyu

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I use the 8bitdo ultimate controller. It is super programmable, the analogue triggers work with dolphin, and it has a nice dock. It has Bluetooth and a 2.4 GHz dongle. 8bitdo also makes a wireless gamecube adapter that connects to an original GC controller. Although I haven’t tested it and it doesn’t mention Linux compatibility