Installing to DIR-853

Hi I have extremely weird router called D-Link DIR-853.
Unable to find any firmware.

I have found some information about it here:
I was able to access it using telnet and got some more information using console:

Looks kinda the same as D-Link DIR-860L rev. B1 so I think it is possible to install LEDE.
Any information how to do it or at list how to setup openvpn?

Both do use the MT7621 SoC...

However, it's never a good idea to install firmware targeted for another router.

I have tried, but it says: "Failed to update the firmware. The firmware file may be corrupted or in incorrect format."
Don't know the way it checks firmware

Closing this topic now.
See linked topic above for continuation.