kernel can't find root filesystem

[M.Hirsch]

I had the same problem with 6.1. But only on some occasions, not always 
(iirc).
The installations I made over the last weeks had all very different 
environments and deployment methods.
I can't tell anymore when it happens and when not because I simply added 
the below loader.conf setting to my postinstall-script.

Add "vfs.root.mountfrom=ufs:da0s1" to /boot/loader.conf to fix it.

HTH,
Manuel