Yo Matt and Benny,
Great to see someone interested in working on this! I worked a little on this last year, but never got past simply compiling for N750. I recall getting stuck at the point where it would not autoconfigure (i think?).
There is only one file that needs to be changed to compile the firmware for the N750. In the file
openwrt_configs/arch_configs/ar71xx change line 3 to `CONFIG_TARGET_ar71xx_generic_MYNETN750=y`.
However, there are more differences that need to be accounted for in the
pre-autoconf etc files and the
post-autoconf etc files. Juul may remember more about the differences between the N600 and N750, but I believe the biggest difference has to do with the layout of the ports/vlans. You could also reference the legacy makenode repo
https://github.com/sudomesh/makenode to see if there are any hints. For example, this
etc/config/network file looks important and it appears to be the only N750 specific file.
Maybe would be a good idea to open a github issue so we can keep this discussion closer to the relevant repository.
-grant (@paidforby)