Blocks is outputting code around content

I’ve a site I’ve had for many years and doesn’t use blocks. I updated to 3.8 and thought I’d try blocks. I set the main field of my blog to block, and created a new entry. I get this. I have no idea what’s missing or where to look.

I had a look at the starter kit where it outputs the page content and copied that (mine had a kirbytext function, now it’s kt). No difference. Help!

        <div class="page-text <?php echo $page->titlefont() ?>">
          <?= $page->text()->kt() ?>

That tries to render your stuff as Kirbytext, use toBlocks() instead.

Thank you.