I'm not sure if its possible for two bluetooth speakers but you can actually connect a bluetooth mouse, keyboard, and earphones at the same time on a tablet.
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And I found how you can connect two audio output by using Samsung's Dual Audio Feature.
To enable this feature: Go to Settings > Connections > Bluetooth. In Android Pie, tap Advanced. ... To use Dual Audio, pair the phone with two speakers, two headphones, or one of each, and audio will stream to both.