Apple runs a fleet of stratum 1 NTP servers at time.apple.com. In my experience, ntpd/chronyd are very happy with them.

It looks like, instead of doing anycast, they maybe use DNS to steer you to the closest one.

time.apple.com is a CNAME for time-osx.g.aaplimg.com.

It's worth noting that this list changes over time, and you're generally probably best off using pool time.apple.com rather than trying to rely on this maybe-outdated list.