Just so nobody else wastes the amount of time I have recently please be aware that the transmission of data over USB 3.0 can cause radio frequency interference to 2.4Ghz WiFi rendering it useless.
It's documented here and in many other places on the net: https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/usb3-frequency-interference-paper.pdf
I noticed that I couldn't connect my single-band (2.4Ghz) Motorola phone to the router and this set me on a wild goose chase having to contact the phone company, ISP, etc all within about 2 weeks.
I tried switching the router to 2.4Ghz (it also does 5Ghz) to see if I had a signal, tried individual SSIDs for each band, changing channels manually, etc, with no solution, but then I noticed on the router's GUI that there was 90% loading on 2.4Ghz with nothing connected!
I'd been running Jellyfin media server on Open Media Vault on a Raspberry Pi 4 with an SSD plugged into the USB 3.0 port. I did a bit of scouting around the net and found RFI on 2.4Ghz from USB 3.0 ports to be a common issue.
So, I plugged the SSD into the USB 2.0 port of the RPi 4 and hey presto RFi is begone. I can now use my phone on WiFi and everything is roses
I should have solved this sooner as I'd noticed a couple of months back that a wireless keyboard would only work with the RPi4 when the wireless dongle was plugged into the USB 2.0 port, it froze when plugged into USB 3.0.
I hope this helps.