I’m posting this for information as we had mixed messages before leaving for Italy.
2 of my children only have (just under) 5 months left on their passports. Before booking Ryanair flights to Italy I checked the gov.uk website and Ryanair website that both stated 3 months left on passports was needed. When we came to check in online with Ryanair, there is tick box to confirm you have 6 months left on your passport. Also stated in several places that you must have 6 months remaining. Various further web searches gave both answers. Calling Ryanair I was told, yes it had to be 6 months and we would not be able to travel. Having already booked airport hotel, parking and Covid tests we decided to try to fly.
(We had our Covid tests with collinsons at Stanstead which were excellent and efficient- they take swabs, email results sent in 30 minutes)
The result is - we are in Italy. No one cared/ mentioned the less than 6 months remaining on the passports.
Incidentally no one asked to see our Covid results (they asked if we’d had them before checking in but no evidence asked for)
Hope this helps someone. We had a very stressful preceding 48hours!