from typing import TypeVar, Generic

T = TypeVar("T")

class FooMetaclass(type, Generic[T]): pass

class Foo(metaclass=FooMetaclass[T]): # error: Dynamic metaclass not supported for "Foo"
    pass

https://mypy-play.net/?mypy=master&python=3.10&gist=d4b169a5ece08ed0607b19fff8e9b749

according to the documentation:

Mypy does not understand dynamically-computed metaclasses, such as class A(metaclass=f()): ...

however this isn't dynamically computed, it's just a generic so mypy should be able to understand it statically