Just a little update:
dmesg -w output is:
[ 5021.594797] usb 1-12: new high-speed USB device number 14 using xhci_hcd [ 5021.743209] usb 1-12: New USB device found, idVendor=2a47, idProduct=201d, bcdDevice=ff.ff [ 5021.743213] usb 1-12: New USB device strings: Mfr=2, Product=3, SerialNumber=4 [ 5021.743216] usb 1-12: Product: Aquaris_M10_HD [ 5021.743219] usb 1-12: Manufacturer: Ubuntu [ 5021.743221] usb 1-12: SerialNumber: FC074240
MTP works fine. I can transfer files no problem.
On my old homeserver running debian buster, adb works (somewhat). I need to try plugging it in a couple of times sometimes. Similar to the installation trouble on the M10.
Thought I'd leave this here for future reference. There is definetly something wrong with the M10 that causes these weird problems though. Thanksfully it has OTG, so I can hook my keyboard up to it.
If a developer wants to maybe try finding out more about the issue, I am up for helping with testing/troubleshooting.