> ReThink DNS often runs into bootstrapping problems

Rethink, the Android app, has a preset list of 5 bootstrap resolvers that you can choose from Configure -> Network -> Fallback DNS. If set to None or System (the default), Android-designated DNS upstream is used (or Quad9 plain DNS is used if it goes missing). You can also set Fallback DNS to Cloudflare (one.one.one.one), Google (dns.google), Quad9 (dns11.quad9.net), or Rethink (zero.rethinkdns.com). Unlike None / System, these use DoH.

> can't find a way to separately configure ... TLS name

You mean, send a different SNI? As in, for domain fronting? If so: https://github.com/celzero/firestack/issues/18

> having a preseeded list of IPs for bundled provider endpoints

This capability exists though we don't expose it via the UI. For instance, ALL preset DNS upstreams (DoH, DoT, ODoH, DNSCrypt), including Fallback DNS, that ship with Rethink, are seeded with IPs at compile time. Given bootstrap DNS (aka Fallback DNS) is already DoH + seeded, the "catch 22" scenario you outline shouldn't come to pass. If it has, then that's a bug we need to fix.