I'm using SSD as well and I know its speed is good since I tested it just after its arrival.
Thanks to your suggesting a different OS I'm coming to the conclusion that its the RPi4. On wireless (once I connected to my private network rather than the public bit I share) pings were 0% lost. Went back to wired and it loaded amazon.co.uk but then speedtest.net disconnected. Transfering multi GB files over wireless is a bit of a none starter - it can be done but....
I've been trying since last October to get this off the ground. First waiting for LibreElec to implement features I needed now this. I think I'll resurrect my Pi3Bs - just watch them decide not to work now.