A technical change (T254295) to the WikidataPageBanner means that any site notice enabled on the site will now display to mobile users as well as desktop users.
Users of projects using WikidataPageBanner are advised to update their usage instructions on MediaWiki:Sitenotice to encourage editors enabling site notices to test and style (or hide!) their banner via CSS on mobile.
If you have any questions about how to do this, please feel free to ping @Jdlrobson on wiki or reply to this tech use notice.
Impacted projects are Wikivoyage, Russian Wikimedia, Catalan, Basque, Galician and Turkish Wikipedia