You need a running board with ubuntu os on the SD card. Please see Radxa howto for that.
Boot device, and login (user: rock | pw:rock).
rock@rockpi:~$ sudo -i
root@rockpi:~# sudo wget https://github.com/radxa/debos-radxa/releases/download/main-d0a80f3b/rockpi-4cplus-ubuntu-focal-server-arm64-20220520-1242-gpt.img.xz
root@rockpi:~# xzcat rockpi-4cplus-ubuntu-focal-server-arm64-20220520-1242-gpt.img.xz | dd of=/dev/nvme0n1
root@rockpi:~# parted /dev/mmcblk0
(parted)
type print
(parted) print
This is the output from the print:
Model: SD SD32G (sd/mmc)
Disk /dev/mmcblk0: 31.0GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 32.8kB 4129kB 4096kB loader1 msftdata
2 8389kB 12.6MB 4194kB loader2 msftdata
3 12.6MB 16.8MB 4194kB trust msftdata
4 16.8MB 554MB 537MB fat32 boot boot, esp
5 554MB 31.0GB 30.4GB ext4 rootfs
We want to remove partition rootfs, which is number 5 from the list, type rm 5
(parted) rm 5
Warning: Partition /dev/mmcblk0p5 is being used. Are you sure you want to continue?
Yes/No? y
Error: Partition(s) 5 on /dev/mmcblk0 have been written, but we have been unable to inform the kernel of
the change, probably because it/they are in use. As a result, the old partition(s) will remain in use.
You should reboot now before making further changes.
Ignore/Cancel?
(parted) quit
root@rockpi:~# reboot`