If you need a public DNS resolver you can use Njal.la DNS.
For IPv4:
95.215.19.53
For IPv6:
2001:67c:2354:2::53
You can use DNS-over-HTTPS with Mozilla Firefox and Thunderbird too.
In Firefox open the about:config page and change network.trr.mode to 2 to use DNS Over HTTPS but keep regular DNS as a fallback. Change network.trr.uri to https://dns.njal.la/dns-query too.
In Thunderbird open Preferences, General tab, scroll down and press the Config Editor button. Change network.trr.mode to 2 (same reason as Firefox above) and update network.trr.custom_uri, network.trr.default_provider_uri and network.trr.uri to https://dns.njal.la/dns-query too.