https://en.wikipedia.org/wiki/Special:Contributions only allows searching one namespace at a time and has no link to an alternative Advanced Search where one could search more than one namespace at a time.
OK, it's either "All" or "one". Not "two", etc.
See T13265: multiple namespace filtering / selection on Special:Contributions (instead of a dropdown) for "only allows searching one namespace at a time".
@Jidanni: As requested before, please read https://www.mediawiki.org/wiki/How_to_report_a_bug before filing tasks: "Include only one problem per task".
I mean
would solve it. Or do all of the above is also an option.