TFTP on network within router

I would like to install a TFTP server on OpenWRT to SSH that would then allow me to push a grub bootloader config to the server. A bit like something here on SuperUser:

It would be useful because even though I have a Rpi the OpenWRT router will already be in place on the Local network to connect the server so it makes more sense to do it this way if possible.

I can compile a Linux kernel myself but I guess there may be some space limitations I haven't looked into (then again it has a USB port on the back of it?) so I am probing around AND/OR any other solutions to solve the same problem.

Has anyone tried anything like this? Thanks for you help!

Hello, I have seen you have boot loaders in packages and grub2-editenv. This will allow me to do the same thing. I will search for tutorials and people speaking about it implementing it. If anyone has any good links please let me know.