You don't consume ostree directly like that, what happens is someone would make Debian ostree-enabled OCI images for users to consume and adapt.
https://opendev.org/starlingx/apt-ostree is one such effort to bring ostree to debian.
https://opendev.org/starlingx/apt-ostree is one such effort to bring ostree to debian.
You might find their forum (intended for end users, not much about development) or some of their repos useful:
I'd be awesome if there was a community effort around bringing the layering functionality and bootc enablement to all of Debian and then we could have our cake and eat it too!