Hello!
Stock image from armbian.com; Armbian_25.8.1_Rockpi-s_trixie_current_6.12.41_minimal.img
Here is the armbianmonitor's output: https://paste.armbian.com/ikodekuzel
The error might be caused by the absence of the f2fs package in the image.
root@rockpi-s:~# armbian-install
Select filesystem type for eMMC /dev/mmcblk0
2 f2fs
<OK>
Formating /dev/mmcblk0 to f2fs ... please wait.
Error: Filesystem tools for f2fs not installed, exiting
root@rockpi-s:~# find / -type f -name f2fs*
root@rockpi-s:~#