Tried a 64gb class 10 card -> didn't work.
Tried a 16gb class 10 card -> didn't work.
Tried a 8gb class 4 card -> didn't work.
I formatted all cards as FAT32 first and then tried exFat, I also tried different allocation sizes (4096b, 32kb, 64kb) -> didn't work.
When I boot the 3ds with the r4i...