“systemctl suspend” when the lid is closed basically the default behavior doesn’t work for some reason
I’d go and figure out why that is instead. Check the journal; I’d journalctl -f before closing the lid and see what happens.
The action of the lid is controlled by logind. Check its config.
If logind can’t detect the lid switch, that likely means there’s some deeper cause that would affect doing the same manually aswell.
Is your laptop docked (or does Linux think it is)?
but that power comes at the cost of not switching between those respective two sinks
Why? How did you set this up?
How are the device(s?) configured?
You might need “Pro” mode to expose separate outputs as such.