ACE3DS Team relased a new product: Ace3DS X. It has a switch for DS mode NTRboot mod.
http://www.digimartz.com/ace3ds-x-support-3dsds-mode_p1311.html
Ace3DS X support DS mode and NTRboot mod
There have a small button on the side of the card, you can puch it to switch 3DS mode and DS mode.
3DS mode-NTRBOOT flashed FLASHCARD.
Ace3DS X has been pre-flashed NTRBOOT and supports installing boot9strap on all 3DS consoles models & versions
The using method of Ace3DS X is a little different from other flashcards, and you need to insert one FAT32 microSD card(maximum capacity is 32GB) to your flashcard
The other steps of using Ace3DS X are the same as other flashcards. Follow the Installing boot9strap (ntrboot) instruction in 3ds.guide.
https://3ds.guide/installing-boot9strap-(ntrboot)
DS mode
The using method is the same as ACE3DS Plus