I had a quick poke at the HA docker image. It’s based on the official python:3.6 image, and a few minutes playing with that show that it also doesn’t have AF_BLUETOOTH support. Strongly suspect the HA docker image will fail for the same reason the hassio image does.
This custom component doesn’t do anything about using the speaker as a media player in HA, sorry. It might be worth seeing if you can get this component running with your setup instead? TTS on Bluetooth speaker via Raspberry Pi