When this topic comes up, I'm always happy to share this incredible lecture from many many years ago about sensor fusion and dead reckoning and how you _cannot_ integrate acceleration twice:
https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s (the whole video is incredible, but this timestamp is the magical bit)
12 years ago I had to write the firmware for an IMU. It took me some real effort to convince my bosses that double integration was, for all practical purposes, impossible. I wish I had known about this video back then...
IMU are very useful to known your orientation though. Even an inaccurate IMU is useful to provide an initial estimate to feed vision-based algorithms.
So you tend to need additional data or assumptions to constrain the double integral?