The ActivityPub Relay at https://relay.masto.social is available to the public. Mastodon and Misskey admins can subscribe at https://relay.masto.social/inbox. Pleroma can subscribe at https://relay.masto.social/actor.
Uptime and availability is not guaranteed, but the intention is to be a stable and reliable relay.
Follow (and optionally set notifications for) @relay for low volume updates and announcements.
masto.social is a general purpose English speaking Mastodon instance.