This might be related to this recent effort https://www.drupal.org/project/drupal/issues/3352256 📌 Move code from the experimental SDC module to core Fixed
But I also see a few very related issues
https://www.drupal.org/project/twig_tweak/issues/3457069
🐛
drupal_view breaks in 10.3
Active
for Twig Tweak which I have on my site. But it also seems to be appearing elsewhere like
https://www.drupal.org/project/adaptivetheme/issues/3460269
🐛
Error after updating to Drupal 10.3.1
Active
which I don't use. So, it might not be limited to just twig_tweak users.
I was able to semi-resolve my issue by identifying a lone string in a render array on the affected page and converting it to [#markup" => "the string"]. I'm still looking for some deeper explanation for this.