See https://unix.stackexchange.com/a/436250 and https://wiki.debian.org/CUPSAirPrint — apparently the AirPrint universal-fallback file format "URF" is patent-encumbered, such that you can't really have a FOSS encoder for it without licensing the patent (just like the MP3 format, until recently.) So OSes that cost money can pay for licenses and so ship encoders, but FOSS OSes cannot.

(I'd nevertheless have expected AirPrint support to exist somewhere in Debian's multiverse repo — but it that doesn't seem to be there. Does nobody have that itch to scratch?)