Advanced features, huh? All of these "cloud DNS providers" are really proud of all the non-standard fuckery they're capable of doing but AXFR from a server or two that I specify? Nope, sorry, can't do that.

As far as DNS goes, that's the only feature I've been wanting for years now: two large anycasted DNS providers (e.g. Amazon Route 53 and Google Cloud DNS) that can slave off of my hidden masters... but that's apparently too much to ask.

Credit where it's due: Hurricane Electric has been providing that service -- absolutely free -- for years now; cf. https://dns.he.net.