What determines relevancy?
The submission must ideally be a blog or article about XMPP/Jabber and/or XMPP-based software (clients, servers, libs).
Some exceptions might be made, for example for a release page showing a new release of some XMPP-based software.
However, marketing brochures (e.g. single-page marketing sites) for new products which don't contain information on XMPP, won't be included.
Extensions and specifications
https://github.com/horazont/prometheus-xmpp-blackbox-exporter (Announcement email https://mail.jabber.org/pipermail/operators/2019-July/003100.html ; docker images available --Jwi (talk) 14:55, 4 July 2019 (UTC))