For years I have been using HA on a degoogled phone and did not have a Google Account, I just had to made it when I needed to commision Matter over Thread devices. Today HA app on Android relies on Android code to generate keys for Matter devices, but this could be achieved the same way if the app itself generated it. Then we would not need this requirement anymore.
Even if it relies on Android libraries I do not think a Google account is needed.
The app apk could be released outside of the Google store and still work the same.
I would like to add to this that I don’t have an android phone or an iphone and currently it’s extremely annoying to try and add matter devices. I haven’t done it yet, but I have spoken to people on discord who have done so using a laptop.
I am by no means an expert on matter, but I believe bluetooth is used in the initial setup so it would be amazing to see HA be able to use esphome proxies for this step.
I have set up a Matter device by connecting a Bluetooth dongle to HA, and bringing the device to HA. No luck with the phone app, even when the ‘full’ app is installed.