Carkus:
I might actually be getting this problem right now. I am just setting up my Starlink today, and have my ubiquiti access point plugged into the Ethernet Adaptor, and then into the Starlink Router. Devices connecting to the Access Point are only getting about 20mbps down on speedtests than standing right next to the Starlink Router and using its WIFI.
Maybe something wrong with my ethernet cables, or setup on the Ubiquiti Access Point.
Hope you can resolve it. Suggest go back to basics and plug Starlink ethernet direct to PC etc. My problem was I got a max of about 100Mbps via ethernet + Google WiFi, rather than 200Mbps normally expected. I was initially using a flat-ribbon ethernet cable. I ended up using a Cat 6 lying around. I do wonder if the Starlink Ethernet needs some decent shielded cable for some reason (e.g. its outdoors-ness). Alternatively going via a switch (as mentioned above) may be a more full-on (but interesting) solution.