I've been using Delta Chat for a while now, on one of my ancient Android devices. I just got it set up on a second Android devices using the same email account, working in sync.
What I did was:
* Install DC on the newer Android
* Set up SyncThing to sync the Downloads folders on both Androids
* Go to Settings > Chats and Media > Backup chats to external storage
* Follow a prompt on the new DC to import the backup, which it searched for and found for me.
I can think of a few ways to make this process simpler and quicker for users. Delta Chat can use QRcodes to add contacts, the same way it's used in Briar. Perhaps QRcodes could also be used to initiate syncing between DC on two devices, as they can in SyncThing?
A QRcode could be generated on the existing DC and scanned using the new one. Assuming both devices are online, keys and chats could be exported to the new device, using the email account as temporary storage for the backup file.
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