Mopidy-funkwhale in iris-docker only works with legacy auth, not oauth

When I use client_id and secret in mopidy.conf, the plugin raises an exception. If I use the legacy api to connect, it works fine.

[funkwhale]
enabled = true
# URL of your funkwhale instance
url = https://funk.local.mytld.com
# this raises the exception:
client_id = myid
client_secret = mysecret
# This works
# username = alex
# password = my-pw

I can connect to funkwhale from iris and play tracks with legacy auth, but not with oauth. In oauth, using (e.g.) search, I get (despite having successfully used mopidy funkwhale login):

Click

dunkel-mopidy | INFO     2021-06-09 16:48:31,048 [8:FunkwhaleBackend-9] mopidy_funkwhale.library
dunkel-mopidy |   Searching Funkwhale for: rolling stones
dunkel-mopidy | ERROR    2021-06-09 16:48:31,055 [8:Core-14] mopidy.core.library
dunkel-mopidy |   FunkwhaleBackend backend caused an exception.
dunkel-mopidy | Traceback (most recent call last):
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/Mopidy-3.1.1-py3.7.egg/mopidy/core/library.py", line 17, in _backend_error_handling
dunkel-mopidy |     yield
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/Mopidy-3.1.1-py3.7.egg/mopidy/core/library.py", line 316, in search
dunkel-mopidy |     result = future.get()
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/pykka-3.0.1-py3.7.egg/pykka/_threading.py", line 55, in get
dunkel-mopidy |     raise exc_value
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/pykka-3.0.1-py3.7.egg/pykka/_actor.py", line 186, in _actor_loop
dunkel-mopidy |     response = self._handle_receive(envelope.message)
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/pykka-3.0.1-py3.7.egg/pykka/_actor.py", line 286, in _handle_receive
dunkel-mopidy |     return callee(*message.args, **message.kwargs)
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/mopidy_funkwhale/library.py", line 349, in search
dunkel-mopidy |     raw_results = self.backend.client.search(search_query)
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/mopidy_funkwhale/client.py", line 121, in search
dunkel-mopidy |     response.raise_for_status()
dunkel-mopidy |   File "/usr/local/lib/python3.7/dist-packages/requests-2.25.1-py3.7.egg/requests/models.py", line 943, in raise_for_status
dunkel-mopidy |     raise HTTPError(http_error_msg, response=self)
dunkel-mopidy | requests.exceptions.HTTPError: 401 Client Error: Unauthorized for url: https://funk.local.mytld.com/api/v1/search?query=rolling+stones

Context

I use Mopidy from the Iris-Mopidy Docker Container, where I added the mopidy-funkwhale extension, based on the readme here, in the Dockerfile.

I will pull this into a dev environment and test myself. Just asking here to see if someone from the maintainers has an idea for the origin of the problem.