In the past, if you broke or lost your phone, your Signal message history was gone. This has been a challenge for people whose most important conversations happen on Signal. Think family photos, sweet messages, important documents, or anything else you don’t want to lose forever. This explains wh...
The current backup system relies on you still having direct access to your phone or a previous backup you moved off your phone yourself.
What Signal is offering now is an automatic backup system that saves an encrypted copy of your data on their own servers which you can access even if you lost your phone and never made a manual backup.
So what the are really introducing is a cloud storage service for the backups, not a backup functionality. I had my previous backups automatically uploaded in Google drive, which, despite fuck Google and all that, was convenient, secure and free.
For what it’s worth, the developers also said the backup system is completely rewritten so that now backups will work across platform and are incremental. Source: https://news.ycombinator.com/item?id=45176074
Incremental is actually a great improvement!
Its basically what matrix does afaik. A encrypted online key backup with a big ass recovery key for restoring that backup.