Hi Robert.

I've notived this problem on my Debian Bookworm machines, which recently
got upgraded to 3006.7 and now I also see this on my OpenBSD -current,
which also started to run 3006.7 minions. I have Salt master running
on OpenBSD -stable with salt-3006.3 and minions after upgrade to 3006.7
lost communication to the master:

openbsd-current-minion# tail -n10 /var/log/salt/minion
The master public key can be found at:
/etc/salt/pki/minion/minion_master.pub
2024-03-05 15:13:22,252 [salt.minion:1157][ERROR   ][44088] Error while bringing up minion for multi-master. Is master at fde4:f456:48c2:13c0::1 responding? The error message was Unable to sign_in to master: Invalid master key
2024-03-05 15:13:32,719 [salt.crypt:1188][ERROR   ][44088] The master key has changed, the salt master could have been subverted, verify salt master's public key
2024-03-05 15:13:32,721 [salt.crypt:803 ][CRITICAL][44088] The Salt Master server's public key did not authenticate!
The master may need to be updated if it is a version of Salt lower than 3006.7, or
If you are confident that you are connecting to a valid Salt Master, then remove the master public key and restart the Salt Minion.
The master public key can be found at:
/etc/salt/pki/minion/minion_master.pub
2024-03-05 15:13:32,727 [salt.minion:1157][ERROR   ][44088] Error while bringing up minion for multi-master. Is master at fde4:f456:48c2:13c0::1 responding? The error message was Unable to sign_in to master: Invalid master key

I didn't check does upgrade to 3006.7 on master help. I don't want
to touch my -stable machines. I could setup Salt master on -current
and test, but all this problem started on Debian and OpenBSD after
minion upgrade to 3006.7. I do follow -stable packages and syspatch
on my 7.4-stable machines, but giving upgrade on Debian and OpenBSD,
I suspect compatibility issue on Salt side.

openbsd-salt-master# sysctl -n kern.version
OpenBSD 7.4 (GENERIC.MP) #3: Wed Feb 28 06:23:33 MST 2024
    root@syspatch-74-amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP


openbsd-salt-master# ls -lhtnr /var/db/pkg/ | tail
drwxr-xr-x  2 0  0   512B Jan 17 23:23 brotli-1.0.9p0
drwxr-xr-x  2 0  0   512B Jan 17 23:23 taskd-1.1.0p5
drwxr-xr-x  2 0  0   512B Feb  7 02:50 ngtcp2-0.19.1
drwxr-xr-x  2 0  0   512B Feb  7 02:50 nghttp3-0.15.0
drwxr-xr-x  2 0  0   512B Feb  7 02:50 nghttp2-1.57.0
drwxr-xr-x  2 0  0   512B Feb  7 02:50 git-2.42.0
drwxr-xr-x  2 0  0   512B Feb  7 02:50 curl-8.6.0
drwxr-xr-x  2 0  0   512B Feb 14 00:47 libunbound-1.19.1
drwxr-xr-x  2 0  0   512B Feb 14 00:47 gnutls-3.8.3
drwxr-xr-x  2 0  0   512B Feb 24 17:56 quirks-6.160


openbsd-current-minion# sysctl -n kern.version
OpenBSD 7.5 (GENERIC.MP) #53: Sun Mar  3 22:36:54 MST 2024
    deraadt@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP


Are you aware of this problem? Ports mailing list, did you notice this,
by any chance?

-- 
Regards,
 Mikolaj