No, List[42] is not currently accepted.

>>> List[42]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/serhiy/py/cpython/Lib/typing.py", line 318, in inner
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/typing.py", line 1127, in __getitem__
    params = tuple(_type_check(p, msg) for p in params)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/typing.py", line 1127, in <genexpr>
    params = tuple(_type_check(p, msg) for p in params)
                   ^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/typing.py", line 184, in _type_check
    raise TypeError(f"{msg} Got {arg!r:.100}.")
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: Parameters to generic types must be types. Got 42.