I’m afraid I have no suggestions for DoT servers.
One tip for your debugging that might be useful is to use dig to directly query DNS servers, to help identify where a DNS issue may lay. For example, your earlier test on mobile happened to be using Google’s DNS server on legacy IP (8.8.8.8). If you ran the following on your desktop, I would imagine that you would see the AAAA record:
dig @8.8.8.8 mydomain.example.com
If this succeeds, you know that Google’s DNS server is a viable choice for resolving your AAAA record. You can then test your local network’s DNS server, to see if it’ll provide the AAAA record. And then you can test your local machine’s DNS server (eg systemd-resolved). Somewhere, something is not returning your AAAA record, and you can slowly smoke it out. Good luck!
The original reporting by 404media is excellent in that it covers the background context, links to the actual PDF of the lawsuit, and reaches out to an outside expert to verify information presented in the lawsuit and learned from their research. It’s a worthwhile read, although it’s behind a paywall; archive.ph may be effective though.
For folks that just want to see the lawsuit and its probably-dodgy claims, the most recent First Amended Complaint is available through RECAP here, along with most of the other legal documents in the case. As for how RECAP can store copies of these documents, see this FAQ and consider donating to their cause.
Basically, AXS complains about nine things, generally around: copyright infringement, DMCA violations (ie hacking/reverse engineering), trademark counterfeiting and infringement, various unfair competition statutes, civil conspiracy, and breach of contract (re: terms of service).
I find the civil conspiracy claim to be a bit weird, since it would require proof that the various other ticket websites actually made contact with each other and agreed to do the other eight things that AXS is complaining about. Why would those other websites – who are mutual competitors – do that? Of course, this is just the complaint, so it’s whatever AXS wants to claim under “information and belief”, aka it’s what they think happened, not necessarily with proof yet.