NullBooleanField was removed in DRF 3.14.0 which affect drf-spectacular ( see PR ). The latest drf-spectacular, or any previous releases for that matter are incompatible with DRF>=3.14.0. More specifically, drf-spectacular should stop using NullBooleanField as it's been deprecated in DRF>=3.14.0 and start using BooleanField with allow_null=True.

I'm unaware wether there are further incompatibility issues with DRF >= 3.14.0 besides NullBooleanField.