We should add an extra "default" parameter to the interwiki table so that interwiki prefixes that don't contain a string after the colon point to the mainpage of the target site, if the default value can be specified. For example, the valueless [[bugzilla:]] currently points towards https://bugzilla.wikimedia.org/show_bug.cgi?id= but if we were able to specify (or choose not to specify) a url string for a hypothetical extra parameter named "default" the [[bugzilla:]] would instead point to the string. And if the string were https://bugzilla.wikimedia.org/ it would not confuse us with an error message of some sort (if it were also some other site). This is somewhat similar to {{#if:{{{1}}} in [[bugzilla:{{{1}}}]]|https://bugzilla.wikimedia.org/show_bug.cgi?id={{{1}}}|https://bugzilla.wikimedia.org/}}. The bugzilla prefix is just an example, this could extend to other sites like google as well.

Version: unspecified
Severity: enhancement
See Also:
T66167: Local interwiki links with no page title should point to the main page