Yeah I honestly don't care how they do it. I just want to export an encrypted blob with a passphrase and import it when needed. Store it on my device so I have to manually move it or store it on iCloud or some other cloud service. I don't care I just want the option to backup and restore!

Not sure about iOS, but on Android it's in settings > chats > chat backup and it creates a backup periodically if enabled. When reinstalling signal one can point it at the backup and enter the code to restore messages.

Unfortunately I am on iOS where there is no such functionality :(

Kind of makes it worse in a way as it clearly shows they do care about backups just not doing it consistently.