See
https://www.riverbankcomputing.com/s...pyqt/download5
I use the pyqt5 12.3 version with no problems with the associated sip for my from source builds of Qt. In fact, you can check out these instructions and replace Qt 5.12.3 with Qt 5.12.5.
https://github.com/Sigil-Ebook/Sigil..._on_MacOSX.txt
Do **NOT** use Qt 5.12.4 as it was broken severely on release and it took me over a month to convince them to fix their breakage! So stick with Qt 5.12.3 or Qt 5.12.5. I have built Qt 5.12.5 but the release version for Sigil uses Qt 5.12.3 which are what my instructions use.
The Qt patches mentioned in those instructions are for Qt 5.12.3 and they can be found in the docs directory of the Sigil project. Qt 5.12.5 makes these patches obsolete.