I'm on the same boat. Unfortunately, I didn't notice Euainb's topic and I created a new one here. I tried your suggestion but still the same issue
@Euainb & @debfido are you using ww.speedtest.net to test the speeds? Are you doing it while connected to the modem via cable or WiFi. If you do it with a cable you should see the full speed if you are doing it by WiFi and you are on the 2.4ghz connection you will not get full speeds but if you have a compatible 5ghz device use that and do the speed test and you should see full speeds.