Pushbullet is described as 'Send links, files, photos, lists, and notes instantly between devices, mirror phone notifications to desktop, and access clipboard syncing with advanced plans' and is a very popular mobile remote control tool in the file sharing category. There are more than 50 alternatives to Pushbullet for a variety of platforms, including Android, Windows, Mac, iPhone and Web-based apps. The best Pushbullet alternative is KDE Connect, which is both free and Open Source. Other great apps like Pushbullet are Blip, Join, ntfy and GSConnect.
Pushover is just a push messaging service and pushbullet will allow SMS, file handling and much more.