A YAML configuration file for Stubby containing a the details of these servers is provided with Stubby and can be found here. This file enables only the subset of servers operated by the stubby/getdns developers by default, users can choose to enable any of the other servers by uncommenting the relevant section.
Note that the Yeti servers use a different root key for DNSSEC! See the Yeti project for more details
It is also known that Quad9 provide service on port 853 for DNS-over-TLS however this is not officially mentioned on their website.