…all that said: adding a non-exstistent SCX-472x and printing a 
test page to it works fine here!

- Which PPD file did you import?  Was it[0]?  If not, try that.
- Why remove foomatic-filters from the default CUPS extensions 
  list?

Customising the extensions field before knowing which driver 
supports your printer is premature.  I recommend removing it 
before continuing, or at least trying more drivers if the default 
of ‘all’ is not an option here.

Good luck!

T G-R

[0]: 
https://openprinting.org/ppd-o-matic.php?driver=pxlmono&printer=Samsung-SCX-472x&.submit=Generate+PPD+file&show=1&.cgifields=show&.cgifields=shortgui