Signal has had the ability to export chat backups for a long time. I'm not sure why people would complain other than the export is local and you have to manage migration to new device by copying files instead of it being saved on a server and uploaded to your new device after you lose an old one.

Also, identity is persistent since you're using a phone number and signal attaches the name you list to that phone number with a registration passcode that must be entered intermittently to keep receiving messages.