What is the reason?

[gdshjzm]

TypeError: unsupported operand type(s) for |: 'type' and '_GenericAlias'

38 │ │
│ 39 │ event_type: EventType │
│ 40 │ params: Optional[dict] = None │
│ ❱ 41 │ returns: Optional[str | List[str]] = None │
│ 42 │ init_timestamp: str = field(default_factory=get_ISO_time) │
│ 43 │ end_timestamp: Optional[str] = None │
│ 44 │ agent_id: Optional[UUID] = field(default_factory=check_call_stack_for_agent_id)

[adrnd]

Found out that you need to make sure you're running Python 3.10 (or higher I guess). Having defaulted to python 3.9 the installation step didn't fully complete it seems, but without any error message. Anyway with 3.10 installed and re-running the Install requirements step I was able to run the server.
But I still don't understand how to get the client running.