RUK do currently “wet lease” RYR aircraft on certain routes (U.K. -> Morocco). I understand that this is a temporary arrangement due to end at the end of the year when the Brexit transition finishes.
Plenty of rumours abound as to what will happen next year. I imagine a few of the new Maxes will be sprinkled around the U.K. on the RUK AOC and given G regs. Company issued a memo suggesting that crews apply for a U.K. licence but offered no assistance and no guidance as to why they’d like us to have both.
We technically have authorisation to switch between RYR and Malta with the press of a few buttons on our EFBs. I wouldn’t be surprised if Ryanair are asking the CAA very nicely for a similar authorisation.