Quick fix for super slow wifi (if you also have Tivo)
I'm sure lots of people have tried this but after suffering super slow speeds for a day and a half, lots of re-boots, changing of channels, turning 2g or 5g off etc, I unplugged the ethernet cable that connected my Tivo box to my Hub. Instantly the speeds were back up to nearly 100mb from less than 1mb.
Tivo is still connected by the co-ax cable so it still works for streaming etc. I'd plugged the ethernet cable in so I could use a remote recording app (which I never used anyway)