Came across this article. It looks like Airplay is getting spatial audio support but they haven't mentioned anything about lossless but I presume that they will include lossless as they need to support 16/48 or 24/48? with 768 Kbps to transmit atmos
www.digitaltrends.com
If @WiiM Support can implement support for Spatial in WIIM Pro Plus or Ultra then we can get atmos downmixed to 2.0 through airplay

Spatial audio over AirPlay could be a game changer for Dolby Atmos
Apple quietly announced that its AirPlay streaming protocol is about to get a big new upgrade.

If @WiiM Support can implement support for Spatial in WIIM Pro Plus or Ultra then we can get atmos downmixed to 2.0 through airplay