Running the following lines with a proper model and frame crashes:

detector = cv.dnn_TextDetectionModel_DB(model=model)
result = detector.detectTextRectangles(frame)

Changing the export type of TextDetectionModel from

class CV_EXPORTS_W_SIMPLE TextDetectionModel : public Model

and recompiling and reinstalling the Python bindings fixes the crash for me
and detector.detectTextRectangles(frame) returns the correct results.

System information (version)

• OpenCV => 4.5.1

• Operating System / Platform => macOS 10.15.7

• Compiler => Apple clang version 12.0.0 (clang-1200.0.32.28)

• Python 3.9.1

• I report the issue, it's not a question

• I checked the problem with documentation, FAQ, open issues,
  answers.opencv.org, Stack Overflow, etc and have not found solution

• I updated to latest OpenCV version and the issue is still there