I don't believe the sprockets and sprockets-rails maintainers (actually it's up to the Rails maintainers, see rails/rails#28430) currently consider it broken. (I am not a committer/maintainer on any of those projects). So there is no point in "waiting for someone else to fix" it; that is not going to happen (unless you can change their minds). You just need to figure out the right way to use sprockets 4 with rails as it is.

I guess I was just waiting for some interest from a maintainer, since there's not much point in wasting my time on developing this if the maintainers aren't even interested in this feature.