>
> I just created a new partition of PLAN9 type there (according to
> https://9p.io/wiki/plan9/setting_up_Venti/index.html), saved and
> rebooted...
>
> ...and system failed to boot:
>
> boot: can't connect to file server: '/boot/kfs' does not exists
>

It seems the boot process does not like two PLAN9 partitions on SD.
Not clear why...

Pavel