There's a ticket for removing mobile.wikipedia.org and wap.wikipedia.org domains/subdomains, which are legacy domain names superseded by m.wikipedia.org and its subdomains.
https://phabricator.wikimedia.org/T104942
The rationale for the removal of these legacy domain names is to help support HSTS preloading in browsers with the existing TLS SAN cert.
After review of the ticket, can anyone think of a compelling reason to keep those old domain names?
I opened a separate thread about this on wikitech-l under a different subject about this as well.
-Adam