

When authentication is down and you can’t figure out the DNS issue, it’s probably time.
You’re absolutely correct; time is like open source software in that it’s just there and works, and corporations don’t consider paying for it or hosting themselves.
The warning section is a good call-out, because it’s one of the services where there’s a good chance your ISP won’t like it.
My opnsense router is configured to send itself as the local NTP server via DHCP and devices are configured to use it for NTP. I don’t have any time critical services like Kerberos auth though. That can give you a starting point for running NTP.