sealing openings and equipment in outer walls.

I don't recall anybody doing long-term testing, but when silicone is on black list, lot of other caulks can be good for boat applications but will not last long with UV exposure.
I think Dicor is safest stuff and easy available.
For interior marine caulks can give you better strength.
I never liked butyl tape. It is heavy and not a good sealer.
I think manufacturers like it because of clear appearance, but you don't hear about so many leak problem on RV without a good reason.