I’m currently updating my MediaWiki from version 1.27 to version 1.35. PHP version is 7.3.
I’ve followed the instructions on updating and everything seems to be fine, except skins not working, leaving me with the plain text and nothing more.

I’ve downloaded the skins versions compatible with the MediaWiki 1.35 and replaced it after the update (cloned from git and switched to REL1_35 branch).
I’ve already checked the skins settings in LocalSettings.php and they seem as they should be, e.g.:

$wgDefaultSkin = 'vector';
wfLoadSkin ('Vector')

The console in Firefox is not showing anything on the matter of an error. The only thing which is showing up only if I’m changing the default skin is this:
Layout was forced before the page was fully loaded. If stylesheets are not yet loaded this may cause a flash of unstyled content
However, it disappears after refreshing the page, but still seems to be related.
Thanks in advance!