How to connect 2 Bluetooth audio headsets to an Android phone?
As in most things, it depends. In this case, since you do not state your device, I will demonstrate from mine, a Samsung 8, running Android 9 (One UI). It explicitly allows dual Bluetooth through settings. If this is your device, click through to it at

Settings &gt; Connections &gt; Bluetooth &gt; Advanced &gt; Dual Audio &gt; ON

The setting allows sound to two different Bluetooth devices.

If your device is different, look for the capability along a similar setting path.