I tried to transpose the QGIS 2 process with no success.
I first had to edit C:\Program Files\QGIS 2.99\etc\ini\python-core.bat which contains references to Python27 instead of Python36.
I run C:\Program Files\QGIS 2.99\bin\o4w_env.bat to properly configure QGIS python environment, but then, when I launch :
"C:\Program Files\QGIS 2.99\apps\Python36\Scripts\pyuic5.bat" -o dockwidget_base.py dockwidget_base.ui
I get this error :
Traceback (most recent call last):
File "C:\PROGRA~1\QGIS2~1.99\apps\Python36\lib\runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "C:\PROGRA~1\QGIS2~1.99\apps\Python36\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:\PROGRA~1\QGIS2~1.99\apps\Python36\lib\site-packages\PyQt5\uic\pyuic.py", line 26, in <module>
from PyQt5 import QtCore
ImportError: DLL load failed: Specified module could not be found.
Similarly, when I launch :
"C:\Program Files\QGIS 2.99\apps\Python36\Scripts\pyrcc5.bat" -o resources_rc.py resources.qrc
I get this error :
Traceback (most recent call last):
File "C:\PROGRA~1\QGIS2~1.99\apps\Python36\lib\runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "C:\PROGRA~1\QGIS2~1.99\apps\Python36\lib\runpy.py", line 85, in _run_code
exec(code, run_globals)
File "C:\PROGRA~1\QGIS2~1.99\apps\Python36\lib\site-packages\PyQt5\pyrcc_main.py", line 21, in <module>
from PyQt5.QtCore import PYQT_VERSION_STR, QDir, QFile
ImportError: DLL load failed: Specified module could not be found.