McDuck I have analyzed the speed tests. Do you have another computer to test, e.g. Windows to exclude your device as a source of error?
Speedtest analysis:
The line is 76% slowed down by your infrastructure. Whether this is the adapter from Apple for the laptops and LAN connection, or your WIFI, I can not tell you exactly. The speed test was done with WIFI. We need a test via LAN cable.
Greetings
Daniele