So I tested this on my XPS 15 with Ubuntu 18.04. The earbuds paired perfectly, and after selecting them in sound I have output. If I put them back in their case, the sound switches back to the laptop speakers, and if I pull them out again, they reconnect and sound switches to them.

I must therefore conclude that something has been broken since 18.04 as it neither worked for me on 19.10 nor now on 20.04.