I've just completed A9LH installation following Plailect's guide and Luma is booting perfectly. I wanted to have Luma and Gateway share sysNAND but I'm getting a black screen when I try to boot into Gateway.
I've formatted my SD with Emunand9's no emuNAND option, I have launcher.dat (tried 3.7.1 and 4.0a) on the root of the SD and Gateway's a9lh payload in luma/payloads renamed to l_gw.bin so I can hold L to boot into Gateway. As I understand it Plailect's guide uses a screen init version of a9lh which Gateway requires. What am I missing?
edit: Got it working. just changed the hotkey, seems L isn't supported.
Yes I had the same setup as you (followed Plailect's guide from Part 3-5) and setup Luma 3DS. I can confirmed that the arm9loaderhax.bin released by Gateway 4.0Beta is working on my N3DS SysNAND 11.x.x. What I did was simply renaming the .bin file to a hotkey that Luma3DS recognized (x_gw.bin) and copy the launcher.dat to the root of my microSD card.
Before getting to this, I saw other guides with long setup instructions that detailed on how to dual boot Luma3DS and Gateway. Correct me if I'm wrong, but perhaps we no longer have to follow those guides if we're using the arm9loaderhax.bin released by Gateway?