Control Bluetooth Device Output?

On the Android phones (I have several, ranging from the latest and greatest S20 Ultra 5G to cheap pre-paid J2s) where I run MiraCheck, I connect two bluetooth devices. One is my headset with a mirophone, and another is a UE Boom 2 speaker (speaker only, no microphone). (This is a non-flying application of MiraCheck, by the way.) Normally, in the Android Bluetooth device settings, the headset is configured to be the output device for calls only; the “Use for…Audio” toggle is off. The UE Boom is configured directly opposite; it is the output device for Audio and the “Calls” toggle is off.

When I connect the headset, Mira will either immediately or eventually speak through the headset. It does not matter which device I connected last, or what combination of the previously-mentioned settings are configured (I’ve tried them all!), the headset always seems to take over. I don’t want it to take over unless I tell it to. I would rather Mira speak to me through the UE Boom 2.

I’ve gone so far as to download third-party and even Samsung applications that are supposed to be able to force applications to route their audio output to different devices. All have failed.

How is Mira coded when it comes to the Android channel for audio output—music, calls, notifications? Is it set to find specific devices it knows are headsets with the well-meaning intention of routing the audio to where it has been programmed to think is best? Is there a way to control the channel Mira speaks through, such as handset, speakerphone, or, ideally, specifiable Bluetooth devices?

Most importantly, how can I ensure Mira speaks to me through my UE Boom instead?