I have tested the 'devel' branch on Debian & Fedora Linux.
The 'mypy_leo.py' part of the ' fullll_test_leo.py' script reports the following errors in both Linux variants:
OK (skipped=3)
mypy_leo.py
leo/core/leoGlobals.py:7603: error: Item "None" of "IdleTime | None" has no attribute "start" [union-attr]
leo/core/leoCommands.py:4819: error: Incompatible default for argument "command" (default has type "Callable[..., Any] | None", argument has type "Callable[..., Any]") [assignment]
leo/plugins/qt_frame.py:585: error: Argument 1 to "keyRelease" of "EventWrapper" has incompatible type "LeoKeyEvent"; expected "QEvent" [arg-type]
Found 3 errors in 3 files (checked 258 source files)
ruff_leo.py
HTH.
Viktor