Are there interrupt Pin in the GY91 Module?
If not, are there good alternative for periodic sensor reading?
(apart from mcu schedule/external timer)
No. The INT pin of the MPU-9250 is not presented on the IO header of the GY-91.
The only way of knowing what is going on inside the MPU-9250 at any time is to go and look. I.e., periodic polling of the sensor.
If you want to use the interrupt pin you will have to shop around for a different module that gives you access to that pin.