@paulyd, you'll always get the same depressing answers about Adobe AIR, as it seems people have decided it was a dead technology, no matter what. But my advice is to check it by yourself, and make your opinion, especially if you are already familiar with Flash.
It really depends on the type of app you want to make. If you want native UI, maybe other frameworks might be more suitable. But if you want to make graphic apps or games, Adobe AIR is very capable.
I'll never understand this developer mindset that says "newer is always better". Personally, I really prefer a mature tech like AIR, than all those trendy solutions everybody gets excited about, but are still very young. I stumbled upon a tweet this morning from Aymeric Lamboley (a respected dev here), who had a nightmare implementing something as simple as in-app purchases in his Flutter app. It seems there is no official solution yet for such a basic feature!
Adobe AIR is rock solid, has regular updates (the Adobe AIR team always pushes updates to deal with all the policy changes from the stores. Until now, they never let us down.) There is a rich offer of native extensions for specific native features... Personally, now that I'm familiar with AIR, my development speed is crazy fast! Everything that seemed complicated proved actually to be easy and simple with AIR.
As a self-employed developer, I always try to anticipate market changes, and invest in "future-proof" technologies. But until now, I didn't find any other solution that supports all the features I need, including native ones, while still providing ease of use and versatility.
Those are my 2 cents. I just wanted to encourage you to check AIR out by yourself. People complain that it is not a trendy tech, but every time a new person is interested in it, they tell him to try something else. Go figure...