So I've managed to steal some hours of sleep and investigate a little more on this... I've tried armbian and several other arm based linux distros (debian, arch, kali) have been a disappointment for the Neo U1. Their device tree blobs (dtb) come from the linux-meson implementation and so far none of them work without issues (closest one was the meson-gxbb-p201.dtb) , most critical problems for me were the network and wifi, first one apparently ok but not responsive at all and wifi wasn't even detected. Look into in the Jan 13 entry from 79bass in armbian forum which is pretty much the same experience I had with this versions.
On the other hand the ELEC distros work quite well on the U1. I have booted CoreElec on it with wifi and ethernet working without major configuration... Problem with these distros is that they are very limited and it looks challenging to install a compiler and package manager, but the good thing is that their dtb has an exact profile for our U1s (gxbb_p200_2G_minix_neo_u1.dtb)
Now I'm looking around for a linux distro that has dtb from the CoreElec branch but with a full set of tools to make it usable.
I'll update if a find something else.
Ok, with the x6 almost everything works when upgrading.
I have another suggestion.
Try the Limbo Qemu emulator in Pl.St ..
In the top right corner in Settings go to HD and ISO Images.
There you get a lot of OS images provided by git. Possibly. there is the possibility to find a correct Linux image that works. Qemu is an emulator.
If the ISO cannot be started, create a dvd / cd boot image and add it to the ISO.
I do that with WinIso and ImgBurn.
Start in qemu do it from CD.
Don't know if it could work?
Please test this for me too, I don't have a U1.