Dejo la respuesta de los foros oficiales de sony, x si alguien está interesado.
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To connect multiple bluetooth devices for any android Oreo and newer phone (I'm using a sony xperia xz3)
1. Go into developer mode (settings > system > advanced > build no. (tap 7 times)
2. Once the developer options menu item displays, select it
3. Scroll down and select 'maximum connected bluetooth devices'
4. Select the no. of bluetooth devices (current is 5)
5. Start pairing your devices with your phone!
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