I read that Ryanair now allows carrying a bag of airport purchases ("duty free") in addition to one carry-on bag, but only in certain airports.
In which airports?
As far as I know Ryanair never stated that it is possible to bring on board an extra bag with the airport purchase, this is what is official.
Anyway, in my personal experience it really depends on the policy applied by the airport: I'm a frequent Ryanair passenger and I only found a single Ryanair airport not allowing carrying on board the duty free shop (Budapest airport).
In a lot of airports (for example Alghero, Pisa, Cagliari, Bergamo) loudspeakers and banners at the entrance of the shops inform the passangers that the airport security allows carrying on board an extra bag. My advice is to look for these banners once you arrive at the airport.
The Ryanair web page “What cabin baggage can I carry?” states as of 2018: “Duty free bags are permitted in the cabin along with your cabin baggage.” This information is not always consistent with the rules enforced by Ryanair ground personnel, for example at SKG.
I KEEP TRACK HERE OF THE AIRPORTS THAT ALLOW TO CARRY ON BOARD THE DUTY FREE BAG, feel free to edit.
Allow: Alghero (AHO, 06/2013), Bergamo (BGY, 08/2012), Cagliari (CAG, 06/2013), Pisa (PSA, 07/2013), Tenerife South (TFS, 03/2013), Gran Canaria (LPA, 07/2013), Alicante (ALC, 07/2013)
Don't allow: Karlsruhe/Baden-Baden (FKB, 04/2013), Budapest (BUD, 07/2012), Thessaloniki (SKG, 12/2017)