From what I experienced, there is no place for SO for Teams where I worked (even if it's a very well designed tool). Either your question is broad and SO is the place to ask, or it's narrow and domain-based then you should store that knowledge somewhere else than on SO for Teams. Regarding where to ask the question in the first place: Slack channels, leading to a Zoom meeting if necessary.
The last scenario I see, which is the "one-time question which might become a recurring question": it is also handled by Slack (good-enough search). And that's the n°1 problem I had with SO for Teams: Slack is good enough, especially if members of your org take the opportunity of such questions to improve the codebase/documentation/internal knowledge base when necessary.