Critical ext_pillar interface qvm_prefs unavailable

My laptop locked up during an update of qubes-os and now I’m noticing the following error message.

[CRITICAL] Specified ext_pillar interface qvm_prefs is unavailable.

I was still able to install debian-10 template and update my fedora-33 one, but I could no longer update whonix nor re-install it.

Any recommended steps to recover from this problem? From searching online I’m suspecting it’s a problem with salt, but I can’t find a way how to reinstall/reset salt for the broken templates.

Have you seen this ?

perhaps you just run linux without xen?
are you fresh install qubes or it has been run for a month or so ?

Yes, it is certainly a salt problem.
You say this is specific to Whonix, but I doubt that is true. It’s more
likely that the Whonix salt calls use something that a basic update
doesn’t do.
Can you take a look in /srv/salt/_pillar and confirm you have
qvm_prefs.py with size 1799 ?

You can always reinstall packages in dom0 using
qubes-dom0-update --action=reinstall ...

You can see the salt packages by searching like this:
dnf list installed |grep salt
You can find out which package produced a certain file by
dnf provides ..

In the end I solved it following the instructions in this comment on issue #2213.

sudo qubesctl saltutil.sync_all
followed by
sudo qubes state.highstate

After this I no longer got the error message about qvm_prefs and I could reinstall whonix and such.