I can not get my Apple TV to connect to my brand new Samsung Q Series soundbar via Bluetooth.
It is recommended to connect the soundbar to the TV (wired), set Apple TV to output audio to the TV (over HDMI), and set the TV to use the soundbar for any audio.
But if you want a direct Bluetooth connection between Apple TV box and soundbar, then it should be done reverse: Connect the soundbar to the Apple TV box: Apple TV is the host where accessories connect to.
Use Bluetooth accessories with your Apple TV - Apple Support
Note that bluetooth is (low bitrate) stereo, and HDMI can be (high bitrate) surround sound.
Additionally, Bluetooth speakers connected to Apple TV are always a temporary configuration, so not default.