Internal server error 500 when trying to add some integrations

I am getting this generic error with lots of custom integrations (eg. the “music” integration in this case - Settings → Devices → Add Integration → Music)

This is what I get in the logs

Logger: aiohttp.server
Source: data_entry_flow.py:398
First occurred: 7:31:13 PM (3 occurrences)
Last logged: 7:43:56 PM

Error handling request
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/aiohttp/web_protocol.py", line 433, in _handle_request
    resp = await request_handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/aiohttp/web_app.py", line 504, in _handle
    resp = await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/aiohttp/web_middlewares.py", line 117, in impl
    return await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/security_filter.py", line 85, in security_filter_middleware
    return await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/forwarded.py", line 100, in forwarded_middleware
    return await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/request_context.py", line 28, in request_context_middleware
    return await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/ban.py", line 80, in ban_middleware
    return await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/auth.py", line 236, in auth_middleware
    return await handler(request)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/view.py", line 148, in handle
    result = await handler(request, **request.match_info)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/config/config_entries.py", line 149, in post
    return await super().post(request)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/http/data_validator.py", line 72, in wrapper
    result = await method(view, request, data, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/helpers/data_entry_flow.py", line 71, in post
    result = await self._flow_mgr.async_init(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/config_entries.py", line 847, in async_init
    flow, result = await task
                   ^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/config_entries.py", line 875, in _async_init
    result = await self._async_handle_step(flow, flow.init_step, data)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 398, in _async_handle_step
    if not isinstance(result["type"], FlowResultType):
                      ~~~~~~^^^^^^^^
TypeError: 'NoneType' object is not subscriptable

I have no idea what this is about. I am getting this with some of the integrations but not with others! Any idea how I can fix this?