Does Fly's Prometheus API endpoint support federation? `remote_read`?

I have Prometheus and Alertmanger (w/ Pusher) configured to monitor various platforms on which I deploy services and alert me if I leave resources deployed. I don’t use Grafana because I don’t need it for this use.

I’d like to include fly.io using the Prometheus endpoint but I’ve been unable to determine whether the API accepts federate|remote_read` requests.

curl \
--silent \
--header "Authorization: Bearer ${TOKEN}"  \
--write-out '%{response_code}' \
http://api.fly.io/prometheus/{$ORG}/api/v1/federate/match[]={__name__=~".+"}" 

And permutations of:

curl \
--silent \
--header "Authorization: Bearer ${TOKEN}"  \
--write-out '%{response_code}' \
http://api.fly.io/prometheus/${ORG}/api/v1/read

Return 400 so I’m assuming not.

remote_read:
  - url: "https://api.fly.io/prometheus/{org}/api/v1/read"
    authorization:
      credentials: "{token}"

If I can configure the Prometheus server to scrape e.g. fly_instance_up, I could configure a rule to alert for it being non-zero.

Or am I missing an obvious alternative?

Thanks!