You could write a dedicated (anonymous) back-end for that,
Thanks! I feared so. Then the strip-HTML-tags approach seems to be the quickest.
if you have a clear idea about what "strip off all markup" means.
Would there be an interest to add that to the core something like a "base class" of exporter backends?
"strip off all markup" simply means export something like "*abc* /def/ =ghi= ~jkl~ +mno+ _pqr_" as "abc def ghi jkl mno pqr". Think of that as a backend without even the minimal adornment that ox-ascii has... and ox-ascii can be a derived backend from this one.