So this is kind of what I tried in https://www.mediawiki.org/wiki/Extension:RelMicroformat, except I only implemented it for the sidebar.

That said, do you really want the link to have rel=me sitewide? Would you be fine with just specific pages?

$wgRealMeLinks = [
    'https://social.example.org/@account' => [ 'Contact', 'Main_Page' ],
];

When you mentioned this initially, I was thinking of stuff like https://wikis.world/@wikisignpost linking to https://en.wikipedia.org/wiki/Wikipedia:Wikipedia_Signpost - but you wouldn't want that to have rel=me on every page that links to the Signpost.

You're quite right. It shouldn't be necessary to have rel=me on every link, and certainly it wouldn't be good to mix it with links on user pages. I like your suggestion of a map for the config.

Regarding the sidebar links, it'd presumably be problematic if they are given rel=me when viewing user pages which also have their own rel=me links.

Change 924768 had a related patch set uploaded (by Legoktm; author: Legoktm):

[mediawiki/extensions/RealMe@master] Support non-user pages through MediaWiki:realme-config.json

https://gerrit.wikimedia.org/r/924768

The on-wiki config sounds like a good idea. I'm guessing a common config would be something like:

{
    "Main Page": [
        "https://example.com/foobar",
        "https://example.org/baz"
    ]
}

Change 924768 merged by jenkins-bot:

[mediawiki/extensions/RealMe@master] Support non-user pages through MediaWiki:realme-config.json

https://gerrit.wikimedia.org/r/924768

Change 926553 had a related patch set uploaded (by Reedy; author: Reedy):

[mediawiki/extensions/RealMe@master] extension.json: Bump required MW version

https://gerrit.wikimedia.org/r/926553

Change 926804 had a related patch set uploaded (by Reedy; author: Legoktm):

[mediawiki/extensions/RealMe@REL1_40] Support non-user pages through MediaWiki:realme-config.json

https://gerrit.wikimedia.org/r/926804

Change 926804 merged by jenkins-bot:

[mediawiki/extensions/RealMe@REL1_40] Support non-user pages through MediaWiki:realme-config.json

https://gerrit.wikimedia.org/r/926804

Change 926856 had a related patch set uploaded (by Reedy; author: Legoktm):

[mediawiki/extensions/RealMe@REL1_39] Support non-user pages through MediaWiki:realme-config.json

https://gerrit.wikimedia.org/r/926856

Change 926856 merged by jenkins-bot:

[mediawiki/extensions/RealMe@REL1_39] Support non-user pages through MediaWiki:realme-config.json

https://gerrit.wikimedia.org/r/926856

Tests unbroken on REL1_39, features in master backported to REL1_39 and REL1_40.

As per https://www.mediawiki.org/wiki/Extension:RealMe, the relevant branch should be used with the corresponding MW core branch

Snapshots releases along with MediaWiki. Master is not backward compatible.

The requires in extension.json still needs bumping (patch above), as the tests in master won't pass on the apparent supported version...

Change 926553 merged by jenkins-bot:

[mediawiki/extensions/RealMe@master] extension.json: Bump required MW version

https://gerrit.wikimedia.org/r/926553

Added to the next Tech News as

The RealMe extension now allows administrators to verify URLs for any page, for Mastodon and similar software. [3]

Please edit directly if tweaks are needed, within the next ~22 hours. Thanks!