I'm working on a hardware/software utility to play Switch/Switch 2 games remotely with my brothers. I found a way to emulate a Switch Pro Controller using a Raspberry Pi Pico based on several different sources (look in the README for more info). I used that to write a firmware for the Pico (with the help of GPT Codex 5.1).
Then I wrote a Python program that connects whatever controller my brothers want to use (as long as it's supported by SDL2.0) and forwards that data from their computer, through Parsec, through a USB-UART adapter, to the Pico, then to the Switch. I then have a low latency capture card (Magewell Pro Dual HDMI I got off of ebay for $100) forwarding the video and audio from the Switch to my PC which I share to my brothers via Parsec. The audio was a bit tricky to get right, and ended up having to use a Virtual audio cable and Voicemeeter potato (a software audio mixer) so that both myself and my brothers could hear the audio.
It works surprisingly well and the latency is pretty low. I even got rumble working! (but not motion controls. If anyone wants to attempt it, I will accept PRs). I haven't done any formal benchmarking for performance, but my brothers and I were able to play Smash Ultimate without too much bother about latency.
You could also use the accessory Python library I made to automate switch controller presses (look in the examples directory). Might be useful for TAS speedruns?
The project is here for anyone interested. It's a bit rough and needs some cleanup and maybe a video tutorial on remote setup. But here is the WIP: