Are your screens working?
I have seen many inexplicable cases of black screen with a9lh, is really brick proof? maybe you need inject your backups with hardmod.
Yes they both work; The Luma3ds config screen shows as well as any payloads and even the recovery mode.
Well this isn't exactly the news I wanted to hear.
The 3DS is still under warranty, however. Would it be an idea to send it to Nintendo if I remove a9lh - would they still know? At this point I just want the thing to work haha.
Thanks.

Did you try using a different version of Luma?Interestingly, sometimes I can hear the system music and other times not, but regardless of how long I leave it, it will always show a black screen.
Also, I don't recall anything out of the ordinary. A day or two before I updated Luma3DS through Luma Updater but that was it, the black screens just came out of the blue a while later.
And yes I have tried pretty much all of them, including #2, and unfortunately none of them have worked. I'm starting to lose hope at this point
Thanks
PS: You can try to install an emuNAND.Try with a formatted SD, with only Luma installed. It can be a corruption/misconfig problem.