@mntmn What's the issue with migrating history? Serious question. My Signal history goes back at least six years now, migrating has never been an issue.
The app creates an encrypted archive on my phone every night, I sync that to another machine using Syncthing. When my phone dies, I provide that encrypted archive and the password to the new device when setting up Signal there. Done.
I can even decrypt it and browse the SQLite database with my messages when I want to.