Hi Chris,
In the November update we have started using an initramfs built into the kernel, which runs before the normal systemd init. One of the things the new script is responsible for is mounting the root filesystem.
The initial release of this initramfs is a little bit buggy unfortunately for USB and possibly NFS installs and there has been a lot of work done on it in the last few days to resolve a few bugs.
Can you please try downloading and installing the external initramfs.gz as described in the following thread:
Ignore the bit about UUID, which is not relevant to NFS.
This will override the built in initramfs with the most current version. See if that solves your issue, if not, please post a screenshot of the exact boot error you’re getting, your cmdline.txt, and if possible the relevant part of your /etc/exports file on the nfs server and we’ll take it from there.
It’s probably just a missing/wrong mount option in the initramfs script that works for some people but not others. (NFS root is working for @sam_nazarko on his test install)
You can see the latest version of this script here, to get an idea of what it does: