I don’t have numbers, but today I think nobody actually uses this. There’s no documentation, it’s tricky to set up and we don’t verify it (it may actually be broken). Adding to that, its maintainers are largely unresponsive. Adding support for new distribution versions and other module versions is very painful.
Because of that I propose to drop it from the installer in Foreman 2.0. We are currently still at RC2 and the major version is a good one to do a breaking change.