Please add "https" to these
$ mech-dump --links https://meta.miraheze.org/ //login.miraheze.org //meta.miraheze.org //www.mediawiki.org/ //twitter.com/miraheze
Indeed, the first three are on every wiki on miraheze.
Besides making them break when the page is saved offline, there are
other reasons too:
https://en.wikipedia.org/wiki/Wikipedia:Protocol-relative_URL
https://www.paulirish.com/2010/the-protocol-relative-url/
https://joonas.fi/2016/12/27/stop-using-protocol-relative-urls/