Update: That KDE/Qt 5.15 DOES have the patches in place to build Qt on M1. If you checkout their tree and replace their qtwebengine with the official QtWebEngine 5.15.7 tree (available from
https://github.com/qt/qtwebengine), you should have something that will build and work on M1.
You can grab the latest Qt WebEngine 5.15.7 plus any new fixes by the following:
Code:
git clone --recursive --branch 5.15 --depth 1 --single-branch --shallow-submodules https://github.com/qt/qtwebengine.git
That you get you something buildable with all of the critical security fixes in a Qt 5.15.7 approximately.