I'm told it's this bug:
https://bugs.chromium.org/p/chromium/issues/detail?id=1164975

and it's related to haveing an old QtWebEngine + new glibc

Fix here:
https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/374232

I think the QtWebEngine package just needs to be updated, but I'll leave
it up to the experts.

I attached a screenshot showing the issue on a github page.
You can temporarily get around the issue with special launch options
(including not using your usual settings)

qutebrowser --temp-basedir --qt-flag disable-seccomp-filter-sandbox