I had earlier written about LEDE 17x install on WNDR4700 here LEDE 17x install on WNDR4700/WNDR4720
Recently, I decided to add a new 4TB drive I had spare with me and while, I was at it might as well move up to 18.06.2 version. I have to say that this version of software install is not only much more polished, it feels like its even faster on the same hardware without any overclocking.
There were only few tweaks I made:
For the multi-wan set up, instead of using wan2, I decided to use wanb. Its possible to delete wanb and in its place add wan2 using luci but I was just feeling lazy.
I added kmod drivers for UAS access to the newer usb drives. The internal drive of 4tb worked like charm. I used gdisk to make partition.
I also had to manually install uPD72020x firmware to get usb3 working.
I did extensively tested to see if the machine will recognize the sdcard, but I was not successful. I would love to try that out and make that work not because I need it but because engineers often do!! And, I promise that if it worked, I will come here and post my recipe for making that work.
Also, I do find that since I have the fan detached, it does get run little hot. I wish I knew or had a recipe to control the fan (switch on only if it exceeded 45 Celsius) and would love to lay my hands on the recipe.
If you guys have any question, do let me know and I can share my experience. And, if you have any pointers to (1) SD Card and (2) fan control, please do let me know and I will appreciate it.