Sometimes freebsd-update doesn't want to update from -STABLE system. Error received would be
Looking up update.FreeBSD.org mirrors... 3 mirrors found.
Fetching public key from update1.freebsd.org... failed.
Fetching public key from update2.freebsd.org... failed.
Fetching public key from dualstack.aws.update.freebsd.org... failed.
No mirrors remaining, giving up.
