If you want “better” and “free” legally, here are three superior alternatives to hunting for an NSP:

The Japanese NSP of Tōnō Training Switch includes some daily sudoku and kanji writing tests that were removed or altered for Western releases. Some players believe the Japanese version trains the brain harder.

Dr. Kawashima's Brain Training for Nintendo Switch not a free game

Dr Kawashima’s Brain Training for Nintendo Switch is a paid retail game, not a free download. While there are no official "free" versions of the full game, you can occasionally find demo versions or sales on the Nintendo eShop Key Game Features Daily Training

Dr. Kawashima's Brain Training: A Fun and Challenging Way to Boost Your Brainpower on the Nintendo Switch

“NEW USER DETECTED,” the text appeared, but there was no cheerful voice-over.