I'm a long-time user of the old Nest Home plugin. The original creator of this plugin did a great job and the plugin was useful for me for a long time (thanks!). The plugin doesn't work for new users and probably because of that, was removed from the Plugin Store a long while ago. The last remaining bits of useful functionality for the few remaining users (including myself) are marked as going away after Indigo 2022.2 due to being coded in Python 2.
I have Nest Protect smoke and CO detectors. I also have Nest thermostats. For what it's worth, I still have my original Nest account (not migrated to Google Home).
I'd be interested to hear if there are any prospects for restoring Indigo support for these devices or failing that, I'd like to hear other users' experiences and advice regarding possible alternatives.