Thanks for those links to patches. FWIW, the KDE community is keeping its own Qt 5.15.X with X > 2 tree with backported critical patches suitable for a LTS release.
You can find more info here:
https://community.kde.org/Qt5PatchCollection
And you can use the following command to checkout the latest KDE Qt 5.15.X tree fully patched:
Code:
git clone --recursive --branch kde/5.15 --depth 1 --single-branch --shallow-submodules https://invent.kde.org/qt/qt/qt5.git
I looked and they are including patches for all platforms including macOS. That said, I have no idea if they have already picked up the arm64 for macos patches or not.