apparently there's a 4.0 kernel version that does away wit- r4i menu
https://sanrax.github.io/flashcart-guides/cart-guides/r4i-sdhc/
do check if this is the exact card or if it's in the target compatibility range. that should patch out the timebomb i think
i cannot help much cause i never had a ds. i only have a ps3 and a wii that are successfully jailbroken and shit
i hope it'll help because the last thing anyone savvy wants is a bricked anything