Their website and F-Droid repo is unreachable now. No update about this on Mastodon and apparently they haven't updated the app in 3 months.
Edit: Some updates from their Matrix channel
Edit2: They responded to the ticket
Thanks for reporting it. The domain automatic renewal failed because the credit card we used for payment was expired, and OpenCollective didn't issue a new card.
The domain is still ours, but the DNS services are suspended. We've already paid for the renewal (11 hours after the domain expired). Unfortunately, our registrar, Gandi, seems to need to take a manual action, and they haven't responded to our support requests yet. Today is bank public holiday in France.