@Jdlrobson, any reason why the file was named like this? Did it have MF skin related hooks in the past?

All hook handlers should be inside includes/MobileFrontendHooks.php
I think the original intention was to keep MobileFrontendHooks.php as a class containing the hooks and no private methods but over time that seems to have failed - MobileFrontendHooks::enableMediaWikiUI for example.

MobileFrontendSkinHooks.php contains helper methods that hooks inside MobileFrontendHooks.php can use that operate on skins.

It would be nice to clean up both of these files and tie them to more meaningful classes. For example MobileFrontendSkinHooks::interimTogglingSupport should probably be a public method on includes/Transforms/MakeSectionsTransform.php since it relates to that code and gradeCImageSupport should be on includes/Transforms/LazyImageTransform.php

The methods getTermsLink, getPluralLicenseInfo, getLicense, getDesktopViewLink, getMobileViewLink , getLicenseText all relate to the footer and is only used inside MobileFrontendHooks::onSkinAddFooterLinks so having a new class with a name like Hooks\MobileSkinAddFooterLinks and then running execute/runHook inside MobileFrontendHooks::onSkinAddFooterLinks would make more sense there like so:

public static function onSkinAddFooterLinks( Skin $skin, string $key, array &$footerLinks ) {
    $hook = new Hooks\MobileSkinAddFooterLinks();
    $hook->runHook( $skin, $key, &$footerLinks );
}

Is that helpful guidance? Let me know if anything doesn't make sense

That's makes sense. I'll break this into 2 sub-tasks then:

1. Move Transforms related code from MobileFrontendSkinHooks;
2. Rename & refactor MobileFrontendSkinHooks.

Thanks for the guidance :)