I'm seeing this on every page view when browsing Wikipedia on desktop, e.g. https://nl.wikipedia.org/
Skipped unresolvable module ext.cx.entrypoints.languagesearcher.init
Most likely it means a module is defined with a mobile target, but unconditionally enqueued on pages. Using target in this way is deprecated and should be avoided in new code.
Migration guide: https://www.mediawiki.org/wiki/ResourceLoader/Migration_guide_for_extension_developers#Target_system