I’d say, since you are experienced with how it feels on a platform, install it on the box spring and see if it seems “right” to you, then consider getting a platform or other foundation.
I just got some plywood cut to size to put where the boxspring previously went on my bed. It’s working fine. My roommate’s mattress is on a boxspring, and it is also working fine. I think as long as the mattress is sufficiently thick, you won’t notice a difference.