I tried publishing with an embedded runtime. It still would not work!
So, if I can't publish an app with an embedded runtime, somewhere in the Adobe code, there must be a check if you are trying to download an apk compiled with Animate, that checks for a minimum supported Android version, ie. it's not just the standalone loaded AIR runtime is lower than the runtime compiled into the app that stops the app loading, the app must also be checking the Android version - Adobe please reply
In the Android part of the app descriptor XML you can set the minimum SDK level, like this:
This has been very handy for times when I've wanted to make sure someone is on Android 4.0 or later. But, it may be worth a try as a way to override the default that AIR uses. You could try using 9 or 10, depending on whether you think your users would have at least gone to 2.3.4.
Or, don't worry about them, they still enjoy your old version!