I recently had a no wifi issue on a switch lite i was working on, replaced the broadcom chip with brand new one, then got some error message. Traced my fault back to the IC highlighted in yellow, not exactly sure what it is though. Im pretty confident both the lite and full size models use the same wifi circuit, so this might be an area for you to poke around in.
Main difference for me is the chip looked like it had suffered overvoltage as I also had to replace the white connector in the top left as well as repair the trace going to the wifi antenna connection. Pretty easy IC to replace, so if you got a donor board its not too much of a hassle.