There was a lot of recording with Dolby EX, which was kind of 5.1 encoding + matrixed rear speakers for the extra 2 channels. They’ll still show up on Netflix as 5.1
The path was identical to Dolby 5.1, with the extra that if you had the right decoder you could tell the 4 surround speakers apart.
AFAIK, Atmos and the DTS equivalent go away from discrete channels by the use of object based sounds. There's no 8.1 or 11.1 or 15.4 channels. It's all up to the decoder now. It's no longer discrete channels, it's discrete sounds in a location and up to the decoder to decide what speakers it goes to.