I have a secret project called "HzRec", but never released it because its performance is utter shit due to the (not overclockable) ARM9 CPU being too slow at bitbanging the SDIO, so it has significantly less FPS compared to streaming via wifi.
But however threre is a HzMod version which can utilize the new2DS's Core3 more due to QTM not running on it, and can achieve up to 50FPS at the best conditions. Sadly due to being optimized to old3DS though, the performance drastically drops when the game is too CPU-heavy
On a sidenote though, you didn't specify what kind of gameplay you want to record. Video? Audio? TAS-like button inputs?
Also, I'd guess NTR can't record more than 30s due to RAM limitations. I'm pretty sure it does some very bad haxxery to be able to record that much video at a decent FPS without being completely bottlenecked by the slow File IO.