Thanks to everyone above - I'm in the middle of converting my first app from APK to AAB and I'd be lost without this thread and the airsdk.dev site!
I'm at the opt in to Play App Signing stage and I'd like some advice about the "optional" step of setting a new upload key. (N.B. Google say this step is "optional and recommended" on this page.)
First of all, is it actually sensible to create a new upload key when I can just use my original app signing key to upload? Everything I've read about it says yes, but I know very little when it comes to this sort of stuff. And nothing I've read is AIR-specific, so I'm worried that there might be some hidden issues with AIR.
Now I have actually tested making a new upload key using the Android dev instructions and got a .jks file out of Android Studio. I could get a key certificate as a .pem file from the .jks, as required by the Play Console for a new upload key, so that was all good.
I then tested signing an AAB with the .jks, (I had thought ADT only worked with .p12 files but this page told me otherwise!) and it seemed to work ok...
So my second question is have I done anything wrong in my above test? I'm out of my depth with this stuff and I'm so used to using a .p12 that anything else just feels weird!