I know this is a reply to an old thread, but I hope this note will be useful. On an Apu2 connected to a cable modem with a gigabit port, I was also getting only 100baseT. After reading the replies to this 2018 post, I checked the cables and found that while the cables were cat8, they were also being run through an old APC Back-UPS for surge protection. Once I connected the PcEngines Apu2 directly to the cable modem, I could resume bathing in the glorious light of 1000baseT.
A hearty thank you to all who replied regarding checking the cables!
