So I made an action for it, changing the document color mode to CMYK, assigning a CMYK profile, flattening etc.
I want the RGB blacks to become
100%K in CMYK. It's
83%C 79%M 73%Y 95%K now.
I looked in Edit > Preferences > Appearance of Black... and set it to Output All Blacks Accurately
I wouldn't like to do it manually for every file, is there a way to interpret RGB black as 100%K by default?