Use qtpy
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QtPy is a wrapper to enable "all" variants of Qt-bindings and version: https://pypi.org/project/QtPy/
Basically, one replaces PyQt5 with qtpy in all files (and update the build dependencies) and it should be good to go.
(Then, tests for different Qt-versions and bindings can be added in a parameterized way, so basically one install different bindings in different runs, but the actual tests are the same.)
Link items together to show that they're related or that one is blocking others.