super().new() is acting differently when (implicitly) inheriting from object versus (explicitly) inheriting from a custom class. This is different from cPython. Initially discovered and reported for circuitpython (I do not have current access to micropython), but the response there said the same symptoms were seen with micropython (MicroPython v1.22.1 on 2024-01-05; PYBv1.1 with STM32F405RG) using my test code. See https://github.com/adafruit/circuitpython/issues/8939

That report focused on some differences in attribute shadowing. Here I switch to showing the differences in raised TypeErrors. I read the python differences information, and did searches of the issue history ("new"). I found a few very old the looked like they might be linked, but they were marked as bug, complete or notimpel. Mostly all of those. Is this a bug, or one of the expected differences that I could not find documentation for?

# bug_test_subclass_super.py
"""check syntax of super().__new__() in different contexts and implementations"""
# pylint:disable=too-few-public-methods
import sys
import traceback

class C1a:
    """base: works everwhere"""
    instance = None

    def __new__(cls, *args, **kwargs):
        if cls.instance is None:
            cls.instance = super().__new__(cls, *args, **kwargs)
        return cls.instance

class C1b:
    """base: fails everywhere"""
    instance = None

    def __new__(cls, *args, **kwargs):
        if cls.instance is None:
            cls.instance = super().__new__(*args, **kwargs)
        return cls.instance

class C2a(C1a):
    """sub: works for cpython"""
    def __new__(cls, *args, **kwargs):
        if C1a.instance is None:
            super().__new__(C1a, *args, **kwargs)
        return C1a.instance

class C2b(C1a):
    """sub: works for circuitpython/micropython"""
    def __new__(cls, *args, **kwargs):
        if C1a.instance is None:
            super().__new__(*args, **kwargs)
        return C1a.instance

def rpt_exc(context, exc):
    """consistent reporting"""
    print(f'{context} instantiation failed:')
    # Be compatible with cPython 3.5 and newer
    tb_str = traceback.format_exception(None, exc, exc.__traceback__)
    print(''.join(tb_str))

def bug_main():
    """run the test"""
    print(f'bug_main: start for {sys.implementation}')
    print('\nC1a')
    tst_in = C1a()
    C1a.instance = None
    try:
        print('C1b')
        tst_in = C1b()
    except TypeError as exc:
        rpt_exc('C1b', exc)
    C1a.instance = None
    try:
        print('C2a')
        tst_in = C2a()
    except TypeError as exc:
        rpt_exc('C2a', exc)
    C1a.instance = None
    try:
        print('C2b')
        tst_in = C2b()
    except TypeError as exc:
        rpt_exc('C2b', exc)
    C1a.instance = None

if __name__ == '__main__':
    bug_main()

Output for circuitpython

>>> from bug_test_subclass_super import bug_main; bug_main()
bug_main: start for (name='circuitpython', version=(8, 2, 9), mpy=517)

C1a
C1b
C1b instantiation failed:
Traceback (most recent call last):
  File "bug_test_subclass_super.py", line 57, in bug_main
  File "bug_test_subclass_super.py", line 22, in __new__
TypeError: function takes 1 positional arguments but 0 were given

C2a
C2a instantiation failed:
Traceback (most recent call last):
  File "bug_test_subclass_super.py", line 63, in bug_main
  File "bug_test_subclass_super.py", line 29, in __new__
  File "bug_test_subclass_super.py", line 13, in __new__
TypeError: function takes 1 positional arguments but 2 were given

C2b

output for python 3.7

% python _hpd/bug_test_subclass_super.py
bug_main: start for namespace(_multiarch='x86_64-linux-gnu', cache_tag='cpython-37', hexversion=50794992, name='cpython', version=sys.version_info(major=3, minor=7, micro=17, releaselevel='final', serial=0))

C1a
C1b
C1b instantiation failed:
Traceback (most recent call last):
  File "_hpd/bug_test_subclass_super.py", line 57, in bug_main
    tst_in = C1b()
  File "_hpd/bug_test_subclass_super.py", line 22, in __new__
    cls.instance = super().__new__(*args, **kwargs)
TypeError: object.__new__(): not enough arguments

C2a
C2b
C2b instantiation failed:
Traceback (most recent call last):
  File "_hpd/bug_test_subclass_super.py", line 69, in bug_main
    tst_in = C2b()
  File "_hpd/bug_test_subclass_super.py", line 36, in __new__
    super().__new__(*args, **kwargs)
TypeError: __new__() missing 1 required positional argument: 'cls'

output for python 3.11

% python _hpd/bug_test_subclass_super.py
bug_main: start for namespace(name='cpython', cache_tag='cpython-311', version=sys.version_info(major=3, minor=11, micro=7, releaselevel='final', serial=0), hexversion=51054576, _multiarch='x86_64-linux-gnu')

C1a
C1b
C1b instantiation failed:
Traceback (most recent call last):
  File "/home/phil/development/workspace/circuitpython/space_clock/_hpd/bug_test_subclass_super.py", line 57, in bug_main
    tst_in = C1b()
             ^^^^^
  File "/home/phil/development/workspace/circuitpython/space_clock/_hpd/bug_test_subclass_super.py", line 22, in __new__
    cls.instance = super().__new__(*args, **kwargs)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: object.__new__(): not enough arguments

C2a
C2b
C2b instantiation failed:
Traceback (most recent call last):
  File "/home/phil/development/workspace/circuitpython/space_clock/_hpd/bug_test_subclass_super.py", line 69, in bug_main
    tst_in = C2b()
             ^^^^^
  File "/home/phil/development/workspace/circuitpython/space_clock/_hpd/bug_test_subclass_super.py", line 36, in __new__
    super().__new__(*args, **kwargs)
TypeError: C1a.__new__() missing 1 required positional argument: 'cls'