official repo uses kernel 4.19 (afaik never updated to include security fixes)…we have now 6.1…there are 3 years between.
i guess ubuntu image created by the repo is old too…my debbootstrap is already ubuntu 22.04
so unpack and flash the image from uboot github-releases (bpi-r64-sdmmc.img.gz), sync and re-read the sdcard (pluging out and in again). you will see 2 partitions: BPI_BOOT and BPI-ROOT
unpack the debootstrap-archive to the BPI-ROOT-partition (root-rights required)
then get kernel-package from my kernel-repo (6.1-main for r64), here you have 2 folders inside: BPI-BOOT and BPI-ROOT…unpack their content to the right partition (itb to BPI-BOOT and lib/modules to your ubuntu rootfs).
then you have to create an uEnv.txt pointing fit-var to your itb-filename
if this all is done you can try booting the board with the card and debug-uart to see if all gets up or you hang somewhere uboot or similar…it is possible that ssh-server is not installed and you get IP-address from your current router…need to configure it to fixed IP