I thought I'd give it a go since it should be possible to build Apple Silicon and Universal on Intel.
First trying the patches for QtWebEngine, I found some files are not there. From what I can tell, the needed updates to Qt5 exist only in 5.15.3+ which is now LTS and commercial only. Maybe it can work somehow in 5.15.2 but I haven't tried a compile yet. Seems there is uproar that 5.15 maintenance is
no longer open source. Later I will see if 5.15.2 works but perhaps it won't. If such is the case, then maybe a AS build is far off.
Perhaps such is a factor that led Kovid to already start the migration to Qt6.
Edit: not familiar with Qt, I found the needed qtwebengine on GitHub. As there is mention of qtbase 5.15.2, though the patcher did not try it, seems like it could be fine. I’ll continue a bit later.