Trisquel on rockpro64

I installed u-boot on the SPI flash. U-boot shows something on the HDMI display if I connect one, but it works much better with a serial connection so this is what I use.

I tried the trisquel netinstaller, it fails to detect the network.

I installed debian on a USB SSD, booted on it and tried installing Trisquel with debootstrap on a micro SD card, approximately following instructions at https://trisquel.info/files/chromebook%20trisquel%2011%20install%20process.pdf. Unlike Debian, this does not put any dtb in /boot, which I suspect is necessary, so I have copied it there manually.

When trying to boot automatically, it is stuck on the u-boot message saying that it is starting the EFI executable.

In manual mode, I did:

=> load mmc 1:2 $fdt_addr_r dtb
=> load mmc 1:1 $kernel_addr_r /EFI/trisquel/grubaa64.efi
=> bootefi $kernel_addr_r $fdt_addr_r

This got me to a grub rescue prompt. I did

grub> insmod normal
grub> normal
grub> linux /vmlinuz root=/dev/mmcblk1p4 ro
grub> initrd /initrd.img
grub> boot

The system boots successfully, I can log in from the serial console, but the network is not working. After some time doing nothing, the system is unresponsive. I saved the output of dmesg and of journalctl. Any suggestion, either on the boot process, or on trying to make the network functional, is welcome.