GC Ultimate
GameCube-style controllers from Hand Held Legend, running HOJA firmware. Pick your model:
GC Ultimate 2: wireless (Bluetooth and WLAN dongle), battery
GC Ultimate 2S: wired
GC Ultimate 1 (Kickstarter Edition): wireless (ESP32 module), battery
Shared guides for every HOJA controller (the app, modes and pairing, updates, settings, troubleshooting) are under HOJA Controllers.