Thanks for all the info so far. Next thing I would suggest trying is a manual curl request to make sure the endpoint itself is working, then if so you can focus on your library’s scrape config and try to figure out why it doesn’t match. See this thread for details on crafting a curl response that works with the /federate endpoint.
The federate endpoint should be able to scrape all metrics, you just need to pass it a selector that matches everything. (In fact, perhaps the selector should be '{__name__=~".*"}' instead of '{__name__=~"job:.*"}' as in your example?)