OpenPGP fingerprint URI scheme `openpgp4fpr` is not supported

SiteSetting Value
allowed_href_schemes openpgp4fpr

Expected behavior

A link to an OpenPGP fingerprint would be accepted and active. See openpgp4fpr URI scheme.

Actual behavior

The link’s href is removed, rendering the link useless.

Note: I also tried the value openpgp4fpr:.+ per Allowed href schemes - #3 by sizeof (but this did not work):