SoundShare for macOS shares audio with multiple Bluetooth devices without any settings, but it costs $1.99 and doesn’t have a trial version.
macOS allows you to play audio on multiple connected devices at the same time. However, this requires some digging into system settings. Alternatively, there’s an easier way.
This issue can be solved with the SoundShare utility, which lets you quickly share audio with all Bluetooth devices without having to fiddle with settings.

Once launched, the menu bar will display a list of currently connected devices, as well as those available for connection. To share the audio, you just need to select the devices for broadcasting and press the “Start Listening” button. The sound will immediately play on all selected headphones.
The utility doesn’t require any additional settings. However, there are some drawbacks: SoundShare doesn’t offer a free trial, so you’ll have to pay $1.99.