The current system python in the docker baseimage is py3.9, while the targetpython and hostpython built by p4a are py3.8, and this was causing linker issues in the pyqt5 build. It is also cleaner IMHO to have p4a handle what is needed for a recipe instead of assuming it is available in the system. (and I think this is how other existing recipes work) fixes https://github.com/spesmilo/electrum/issues/8016