I started playing in 19w08a  in this map, mobs spawned sheldom but they did spawn.

When I downloaded the last snapshot no mobs were spawning but the raid mobs with the flag... 

I checked the gamerule doMobsSpawn and my difficulty a couplr of times :3

I just wanted to submit this just in case is not a isolated case.

PD: I built a grinder to check if it was a low spawn rate or no spawn rate, no spawnrate is detected

Thanks XoXo