I tried again. An APK file did download to Android phone (Samsung S21 5G Android v15), I went through the procedures again with some success this time. I now have ASIair 2.3 firmware 41.63 on the Android.
I also tried on the iPad (OS 18.6.2, 9th gen). The outcome was slightly different. I now have ASIair 2.4.9 firmware 41.63 on the iPad.
I guess one of them must be wrong. I can’t test either until a clear night so will keep both on for now.
Thanks for your perseverance.