I have Luma3DS installed, but I could never switch to emuNAND.
Before I have A9LH installed, I could still switch to emuNAND normally.
Are you not suppose to use emuNAND alongside with A9LH?
To use emuNAND with a9lh you need to switch off updated sysNAND in luma settings (access by holding Select at boot up).
EmuNAND came around because you used to have to keep sysNAND below certain firmwares to keep hacks (previously 4.5, then later 9.2). This prevented you from playing newer games that required higher firmwares. But then emuNAND allowed you to run a higher firmware system while keeping the real system exploitable.
Now that you can update your sysNAND using a9lh, the need for emuNAND is gone. In fact, it has several disadvantages: 1. Requires space on your SD card, 2. GBA games must be installed twice, 3. If you change SD cards you have to create an emuNAND on the new card, backup emuNAND on the old card, and inject the old emuNAND backup to the new card as well as copying files, but with a sysNAND-only system you only have to copy files, 4. If your SD dies, you lose your system (Miiverse data, activity log etc) as emuNAND is run from the SD card (if you took a backup you can restore it, but lose any progress between then and now), 5. Using an emuNAND is hard on your SD card (many reads and writes) which will cause it to die faster. So far I've never seen anyone's NAND die from too many reads and writes in the five years the 3DS has been out so it's obviously made of tougher stuff.
This is all I can think of right now but there are other disadvantages too. And really no benefits. With Decrypt9, safety isn't a concern anymore.
Edit: there's one benefit, having a region-changed emuNAND so you can effectively have multiple consoles on different regions, for whatever use that is to you.
