@sesivany Just playing around and selected input from my headphones and it dropped the audio down to HSP/HFP. Ouch. It's possibly even worse than a walkie-talkie.
(This is a shortcoming of Bluetooth audio. There's no hi-res (or even medium-res) audio output with input at the same time, sadly. Thankfully, it's easy enough to switch back to A2DP with LDAC... even in GNOME settings.)