Updating this, same friend but a different person now behaving towards him in a manipulative manner.

It’s helpful to come back to this and reread the replies. I decided not to get involved at all this time.

What I notice is he keeps returning to the topic, describing something which has obvious red flags (to me) and talks it up but his body language and voice tone clearly show he’s uneasy - another friend has noticed it too so it’s not just my perception.

I feel like it’s dangerous territory for me, like I could easily say the wrong thing, so what I’m doing is staying very quiet, allowing him to talk but changing the subject once he’s done.