The `useskin` parameter should work on any MediaWiki instance as long as the targeted skin is installed on the instance. You can grab the list of skins from:

Special:Version (example: https://en.wikipedia.org/wiki/Special:Version#mw-version-ski... )

An API query: * direct: https://en.wikipedia.org/w/api.php?action=query&format=json&... * demo: https://en.wikipedia.org/wiki/Special:ApiSandbox#action=quer...

Which yields the code name of each skins installed (eg: vector-2022, vector, monobook ...).