On fedora 28 beta I had a strange problem with Epson L355 (and probably other epson printers).
Installation of propriety epson driver went smooth and without any problems but printer drivers were not detected/visible on driver list.
After some research I have found that ppds files that are compressed with gzip (ppd.gz) for any printer driver aren't accepted anymore by cups (dont know if they were before).
After uncompressing them, all started to work and seen on printer driver list.
Just wanted to share my experience