I'm using 2.4.25, but short of trying every one of the official andCheck against OpenLDAP 2.4.25. I believe nearly all backends and overlays support slapd-config now.
contrib overlays one by one, I don't know of any way to find out which
ones don't support slapd-config. That's why I was asking: I was hoping
someone knew what the holdouts were, or knew where it was documented.