I’m probably going to get some of this wrong, James, but I’m sure I’ll be corrected which is cool.
Apple is not making this easy. My understanding is that an iMac (with OS) will do it, but does not have an “exclusive mode”, so whatever setting you have in your MIDI setting is what will be applied to the bitrate across the board. You’ll need to go in and manually change it each time the bitrate changes.
iOS on Apple devices will do it through the Apple Music app, but Bluetooth and Airplay can’t do hi-res, so it will need to be hard wired and hi-res will need an outboard DAC (versus lossless).
The Roon community has a lengthy discussion on this, with plenty of people trying different combinations of hardware and connectivity to see what works.
Darko also did a video on what combination of things will and won’t work to provide lossless/hi-res.
That’s all I’ve got because my head is kind of spinning with all this!