Sorry I've not heard of this happening before. I'd contact Nintendo and get it looked at.
Ouch I was hoping this wasnt the case but I actually tested it out again today and low and behold, Im getting 37Mbps down and 8Mbps up.
I think thats ok for now!
Is it worth trying with another wireless network (even just tethering your phone for 10 mins) to see whether it changes? That'll tell you whether it's the Switch or the network.
(I appreciate you've tested the network with other devices, but doing it the other way around can't hurt either).
You know, I should have done this and it never crossed my mind! Good idea for next time, thanks.
My first switch had awful WiFi range and speeds, I would send it to Nintendo and make I clear as day thats it's a WiFi issue not wireless controller issue. As I sent mine in 3 times they thought i sent it in due to joycons .... Muppets... I ended up replacing it with the retailer.
If your playing docked I would rerecomme getting usb Ethernet adapter I have ugreen one it's great.
Hmm interesting, do these just plug into one of the USB sockets? Is there any configuring or anything like that on the Switch? Does it detect it immediately as a network device and connect an ethernet to it?