I’m running Fedora 33 and I asked myself the same question.
Perhaps unbound-anchor.service is run before internet connection is estabilished? Should it be run after NetworkManager-wait-online.service?
journalctl -u unbound-anchor.service shows the time needed to start it for each reboot.
I see in my logs that sometimes it’s very quick (less than 1 second) and sometimes it takes about 18 seconds:
-- Reboot --
nov 06 00:00:29 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 06 00:00:29 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 06 00:00:29 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 07 00:01:02 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 07 00:01:02 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 07 00:01:02 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 08 19:04:58 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 08 19:05:16 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 08 19:05:16 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 10 23:24:46 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 10 23:25:04 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 10 23:25:04 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 11 00:00:28 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 11 00:00:28 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 11 00:00:28 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 12 18:33:52 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 12 18:34:13 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 12 18:34:13 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 13 16:40:10 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 13 16:40:28 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 13 16:40:28 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
-- Reboot --
nov 14 23:29:18 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 14 23:29:36 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 14 23:29:36 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.
nov 15 00:01:01 localhost.localdomain systemd[1]: Starting update of the root trust anchor for DNSSEC validation in unbound...
nov 15 00:01:01 localhost.localdomain systemd[1]: unbound-anchor.service: Succeeded.
nov 15 00:01:01 localhost.localdomain systemd[1]: Finished update of the root trust anchor for DNSSEC validation in unbound.