Here is the first draft at a Nintendo Switch (NS) compatible gamepad for Teensy LC/3/4. Similar projects exist using 32u4 and LUFA but this is an implementation for Teensy LC/3/4.

I added support for using the Teensy 3.6/4.1 USB host port so other game controllers can be used with the NS. For example, a Thrustmaster T.16000 flight control stick can be used as a one hand NS game controller. Or use an XBox One controller on the Switch.

https://github.com/gdsports/NSGadget_Teensy