I’ve recently done the same thing. I setup both dendrite and synapse.

For both I tried the srv record and could not get it to pass the federation testers. In the end as mines behind a nginx proxy I served the wellknows frommnginx rather than letting synapse/dendrite serve it. Federated correctly afterwards.

As such I would suggest serving the json well know using whatever reverse proxy you are using.

It’s Scavenger Studios, and the game is Seasons.

In case you didn’t want to click the link to see who it was.