We have a Linux CUPS server which we install our printers to. We then point the Google Admin Printers to install the CUPS server's printers. This removes the need for PPD files on the Chromebooks.
CUPS isn't perfect, we do find that jobs can get 'stuck' and that PPD files don't always exist for printers.
This architecture gives our Chromebooks print options natively.
I'm not a fan of papercut mobility print, printix, etc, as most don't provide print options.
DirectPrint.io which is now Coreza Print, has been pretty good so far. We may end up moving to them to ditch our on-prem print server, more to come on that.