Nintendo Switch Modding - Step One - RP2040 Firmware Install
This video shows how to connect a RP2040 chip via USB and install the latest firmware. I can NOT show you where to get the fw_2.73.uf2 file, but it is out there if you google it. This process is necessary for you to be able to launch custom firmware on your switch. Of the dozens of these I have come across NONE of these PicoFly clones have shipped with firmware actually installed. Luckily its easy and only takes a minute.
Link to minimum microscope I would use($80-85 depending on coupon): https://amzn.to/3Sq8q3Y
(I tried a few cheaper ones...this is the cheapest one that was useful enough ...you can always go nicer!)
Link to a perfectly capable $13 soldering iron: https://amzn.to/3SPbh80