Would be really great to hear more on what determines the spawn rates of these mobs to help us determine what is going wrong here.
Since the 1.14.3 version was marked as duplicate add it to the affected versions
Also experiencing this issue
Small edit: They still spawn in swamps correctly from what I can tell
Zanthous M
Would be really great to hear more on what determines the spawn rates of these mobs to help us determine what is going wrong here.