How can I reflash a Dlink DPN R5402 router?

Question

Firmware

Please tell me, I have a castrated router (modem, terminal) of PON technology from Rostelecom installed at my house, the essence of the question is how to call the full potential from this router, how can I flash it so that it does not work with Rostelecom's firmware, but with my personal one and so that no one had access to it except me? Otherwise, I'm paranoid and don't like it when technical "specialists" tamper with my hardware, which in turn runs my home PCs and home server.
Tell me the solution to this problem, so far I have found only one solution .. I made a bridge between this miracle and Dir 300 WWRT in Wifi client mode, but it is very problematic to do port forwarding because I do not want all ports on any of the routers to be open. Is there a solution to my problem? Surely someone has already encountered a similar problem.

Answer 1

I'm paranoid and I don't like

With this to the doctor ...
The equipment is not yours, but Rostelecom's, and all this is spelled out in the contract.
Connect your Dir 300 WWRT with a wire to your modem and do whatever your heart desires with your router!