Comment # 1 on bug 1176023 from Fabian Vogt

That bu(In reply to Ahmad Samir from comment #0)
> the issue affects Debian too,
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=962811
> 
> The issue seems fixed by updating python3-qtwebengine-qt5, I tested by
> building PyQtWebEngine-5.15.1.dev2008221426.tar.gz from upstream.

That bug has the following comment:

> I've done a bit of digging, and this problem is solved by manually
> updating pyqt5webengine to 5.15 from unstable.  The root cause is that
> there is an unstated strict version dependency between these two
> packages, and/or some symbols were changed without being handled
> properly.

We have version 5.15.0 of both though, so if it's indeed a symbol change issue
it's some kind of upstream issue...