I don’t have the Costco KS6 but I have the Oticon OPN which is also made for iPhone and stream via the Apple proprietary BLE protocol.
Oticon also has an ON app made for Android to allow OPN users to control the OPN functions from their Android phones via Bluetooth, but you still cannot stream audio to the OPN from Android phone. So Bluetooth control is doable and already done. It’s the BLE audio streaming that’s still not doable on Android yet.
Apparently there’s no BLE audio streaming standard for Android yet so that’s why the HA mfgs cannot support audio streaming for Android due to this lack of standard, while they do support the audio streaming from iOS 9.3 or later already. Actually I heard from somebody on this forum that the BLE audio streaming standard has recently been finalized already (in BLE 5?), but it’ll take time for Android phone mfgs to adopt. And HA mfg then can support this new Android BLE 5 standard. But I only heard it from somewhere on this forum and can’t vouch for the validity of this rumour.
So even though the OP of this thread is a SW developer, I’m not quite sure if he can simply develop an app on the Android side unilaterally to stream to the HAs at this time unless he knows what the Apple proprietary BLE protocol is and mimic that because that’s the only protocol the HA mfgs support right now. That’s probably why the OP never got anywhere with this.
And when the Android phone mfgs finally support the new BLE 5 standard for HA direct streaming, then I’m sure the HA mfgs will start supporting direct streaming on Android phones using this new standard protocol. But I think that has to be the order of things to happen: the Android phone mfgs must support the new BLE standard first (because there may be hardware changes involved to the phones, not just SW only) before the HA mfgs will jump on the Android phone’s bandwagons.
I don’t think it works the other way around where HA mfgs declare they support the new Android BLE standard and wait for third party hackers/developers like our OP to develop apps on Android phones to work for the HAs. The HA mfgs don’t lack their own SW developers to develop their own Android apps, but the new Android BLE standard has to be supported by the Android phone mfgs first before HA mfgs can make Made for Android on their HAs a reality.