50mm "Normal" Lens... Ok, but "Normal" on FF or APS-C Sensor?

If you want to debate "normal" should we also try to debunk "wide angle" and "telephoto"?

40-60mm lens on FF is typically said to be "normal" because in typical shooting and viewing conditions it results in a perspective that is similar to what our eyes would see.   You can come up with scenarios where it is wrong, but in most scenarios it works out that way.

To answer the OP: 40-60mm on FF, 28-40mm on APS-C, 20-30mm on 4/3 are all normal primes.