You don't have to use the cloud transfer with WhatsApp. You can simply transfer the backup files manually before you do the first logon. They're in the media folder.
> You don't have to use the cloud transfer with WhatsApp. You can simply transfer the backup files manually before you do the first logon. They're in the media folder.
This does not work anymore. The chats are encrypted and the key to decrypt them is not in the backup files.
I tried the exact same thing a few weeks ago with a de-googled phone and it did not work. I had to transfer the /data/data/com.whatsapp folder as well via root access, then it restored the chats (the display of the old phone was dead and hence I couldn't initiate any kind of account transfer to a new phone).
Weird, for me it worked fine. I didn't need to transfer the root parts. Nor did I do anything else on the old phone. I just signed in on the new one with the backups in place.
I don't use Google services or an account either, though I do have Google play installed.
With Viber I don't know, I've never used that.