https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108062
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- You still aren't showing the code that gives this error, so I'm just not going to bother reading your big reports in future PNM_COLOUR_SPACE cannot be formatted because there is no std::formatter<PNM_COLOUR_SPACE> specialization.