Customising widget titles/headings in WP 5.8

So I have updated WP to 5.8 and the widget titles are no longer being recognized from my customized functions.php

'name'          => __( 'Sidebar 1', 'mytheme' ), 'id'            => 'sidebar-1', 'before_widget' => '<div id="sidebar">', 'before_title' => '<h1 class="sidebar-title"><span>', 'after_title' => '</span></h1>', 'after_widget' => '</div>', 

I’m racking my brains and I can’t seem to solve it because it’s a new change and no one seems to have asked this anywhere. My widgets want to have <h2>Title</h2> no matter what I put in functions. There is no sign of my H1 class. Plus massive spaces/padding because I think the titles ("headings" now apparently) are outside of my widget blocks. If i revert back to an older WP version, it works just fine. I can’t use any plugins. Am I missing something obvious?