OK, i ran a few more test.
if I try reinstalling mlmmjadmin it try to install py-pip and fails (because it is already installed).
it turns out that the upgrade script looks for /usr/local/bin/pip3 (in FreeBSD) while the installation actually place it in /usr/local/bin/pip.
if i call pip -V it is using python38, the same as everything else, so it is correct.
I created a symbolic link at /usr/local/bin/pip3 and the reinstallation completes successfully but still will not start.

Now when the installation try to start it i actually get an error:

Starting mlmmjadmin.
[uWSGI] getting INI configuration from /opt/mlmmjadmin/rc_scripts/uwsgi/freebsd.ini
* Sync mailing list profiles to SQL/LDAP.
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 174, in _new_conn
    conn = connection.create_connection(
  File "/usr/local/lib/python3.8/site-packages/urllib3/util/connection.py", line 96, in create_connection
    raise err
  File "/usr/local/lib/python3.8/site-packages/urllib3/util/connection.py", line 86, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 61] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 699, in urlopen
    httplib_response = self._make_request(
  File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 394, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 239, in request
    super(HTTPConnection, self).request(method, url, body=body, headers=headers)
  File "/usr/local/lib/python3.8/http/client.py", line 1256, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/local/lib/python3.8/http/client.py", line 1302, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/local/lib/python3.8/http/client.py", line 1251, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/local/lib/python3.8/http/client.py", line 1011, in _send_output
    self.send(msg)
  File "/usr/local/lib/python3.8/http/client.py", line 951, in send
    self.connect()
  File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 205, in connect
    conn = self._new_conn()
  File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 186, in _new_conn
    raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x802a42370>: Failed to establish a new connection: [Errno 61] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 439, in send
    resp = conn.urlopen(
  File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 755, in urlopen
    retries = retries.increment(
  File "/usr/local/lib/python3.8/site-packages/urllib3/util/retry.py", line 574, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='127.0.0.1', port=7790): Max retries exceeded with url: /api/messengers-ny@lists.silomessage.org (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x802a42370>: Failed to establish a new connection: [Errno 61] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "tools/sync_profiles_to_db.py", line 244, in <module>
    qr = get_profile(mail)
  File "tools/sync_profiles_to_db.py", line 140, in get_profile
    r = requests.get(url, headers=api_headers, verify=verify_ssl)
  File "/usr/local/lib/python3.8/site-packages/requests/api.py", line 76, in get
    return request('get', url, params=params, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/requests/api.py", line 61, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 542, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 655, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 516, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='127.0.0.1', port=7790): Max retries exceeded with url: /api/messengers-ny@lists.silomessage.org (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x802a42370>: Failed to establish a new connection: [Errno 61] Connection refused'))
* Upgrading completed.
<<< NOTE >>> If mlmmjadmin doesn't work as expected, please post your issue in
<<< NOTE >>> our online support forum: http://www.iredmail.org/forum/

Now this actually happens every time i upgrade mlmmjadmin.
My installation is inside a FreeBSD Jail, so 127.0.0.1 does not exists. localhost is the IP address(es) that the jail was given. So i always need to exit the /opt/mlmmjadmin/rc_scripts/uwsgi/freebsd.ini and insert the correct IP in place of 127.0.0.1 for http-socket.

Once this is corrected usually it starts without issues, but now it doesn't.

Any help is appreciated.