When I try to save changes in MediaWiki:Common.css:
[exception] [770bdd4cea9ac01076a374ad] /w/index.php?title=MediaWiki:Common.css&action=submit MWException from line 587 of /var/www/withoutvowels/web/w/includes/content/Content Handler.php: Format text/css is not supported for content model wikitext
MediaWiki 1.31.3