https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120676
--- Comment #2 from Nathaniel Shead <nshead at gcc dot gnu.org> --- Ah, I see you actually already reported almost exactly this in PR114990 :) The message is still "hopefully will be fixed for the next major release" but I personally have very limited time for OSS things, and it doesn't look like anyone else really has availability or interest in GCC's modules support, so maybe don't hold your breath too long!
