Recover whatsapp chat backups after reset without access to old number I made a factory reset of my phone, which had Whatsapp linked to a deprecated phone number. 
Before the reset, I backed up the chats both on Google drive(*) and on the simcard (a crypt12 file).

I hoped I'd be able to recover the chats after signing in with my new phone number, but this isn't happening on its own.

Furthermore, I can no longer log in with the old phone number (as it is deprecated), and cannot do the number transfer.


Is there any way to force a recovery of previous whatsapp chats on a
phone with a new number? 
If not, is there at least a way to access the text content of the
backup files (either on Gdrive, or on the sd card) from e.g. a
computer, or are all the chats definitely gone?


(*)a similar question was posted here, but is unanswered and only refers to restoring from gdrive, whereas my question also mentions a local backup, and the ability to access the chats even from a different platform as whatsapp.
The WhatsApp backups are encrypted with a key which is connected to your account. This ensures that the backup only gets restored if the user connects the same phone number. If not, this backup holds zero value for WhatsApp. 

This also means that the database backup (on your SD) card cannot be read. So, you shall not be able to decrypt and bring it to a readable version. I'll really look for possibilities of getting the old number re-issued or something. 

Without access to that old number, there's no chance (as per my knowledge) to decrypt the database and restore it or make it readable.