I agree that there aren't really any great solutions. But the alternative is that Signal stores your data. I think this would make a lot of users very upset and compromise part of Signal's core mission.
This is one area where, and I know what you're going to say, but Matrix actually does really well. My data, on my server, in my house, not tied to any specific single device I own but distributed across several and backed up in an encrypted manner.
But you've got me thinking about the data export option. Saturday is coming. Hmm...
I'm actually a fan of Matrix. I just see Matrix and Signal as different tools. You're probably aware of it, but if not, there is a Matrix bridge for Signal.
> But you've got me thinking about the data export option. Saturday is coming. Hmm...
Hey, I'm really hoping it works. Let me know how it goes!
As far as I know the backup is encrypted.
> Are you not able to import these backups into the desktop client?
No, the desktop client is not standalone, and ONLY syncs with the a phone to get content. Moreover, if you don't use the client for a period (2-3 weeks in my experience?) it de-syncs that desktop client. Re-connecting that desktop to your phone will only sync messages starting as-of the connection, so there's no way to get the desktop app to pull your whole history. (This is another gripe I have about their sacrifice of actual usability for security that only helps a few very specific use-cases.)
You're probably rigth about hacking something together. Someone has created a library [0] allegedly for decoding the backup files. Friday night is D&D night though, so I haven't had the chance. :-)
[0] https://github.com/pajowu/signal-backup-decode