Short answer
HubSpot's KB: Notetaker is off by default until a Super Admin turns it on. It always posts a chat message on joining; the audio announcement can be turned off. If an invitee doesn't consent, it won't join.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
Check recording laws where your attendees are.
3. Related
Notetaker in Zoom and settings.