An open-rank position means that:
the search committee will consider applicants across career stages.
What's the translation of "open-rank position" in French, in the context of a job post?
Linguee didn't help. Google translate didn't help. Google translate did suggest "rang ouvert" but I barely saw any use of it and some places use it with a different meaning, e.g.:
Rang ouvert (professeur adjoint)