The BeforePageDisplayMobile will be deprecated in 1.43 (T350200).

A usage was detected in the Wikibase codebase here:
https://gerrit.wikimedia.org/g/mediawiki/extensions/Wikibase/+/31782c68e53239618eb59b2f4574fc93d1d6b87e/extension-repo.json#969
Please update it to use the BeforePageDisplay hook. Thanks in advance!

The preferred way to do this is to use the BeforePageDisplay hook as follows:

$isMobileView = ExtensionRegistry::getInstance()->isLoaded( 'MobileFrontend' ) &&
			$services->getService( 'MobileFrontend.Context' )->shouldDisplayMobileView();
if ( $isMobileView ) {
  ..
}