What Happened to Pushbullet?

There's a very handy app called Pushbullet (https://www.pushbullet.com/) which allows you to send urls/text/files from one device to another. It also has an ability to sync SMS and notifications. I've been using it for several years now.

It looks like it has been transitioned into a passive maintenance mode. The app still works, but there haven't been any updates to the Firefox extension since 2020 (https://addons.mozilla.org/en-US/firefox/addon/pushbullet/versions/). Anyone knows the reason? Their blog doesn't seem to explain that. I'm afraid it may stop working at some point.