Python has type annotations since 3.5 and you can get static type checking via mypy. This is a type system that works quite well IMHO and eleminates most of the issues you mentioned.
> Mypy mostly seems immature, buggy ...
That was my experience some time ago as well, but it's getting better from release to release. Look at the repo [0], it's continuously improving. I find Mypy deserves more recognition.
The same guys working on mypyc [1], which I think is very interesting too.
[0]: https://github.com/python/mypy/graphs/contributors [1]: https://github.com/mypyc/mypyc
Either some weird support library hasn't been upgraded to 3.x yet or some expensive piece of software/hardware can't be accessed with Python 3.x