@hokkaidofishfilms, Fusion files have to be stitched using the Fusion Studio on a computer. You can also utilize the GoPro Quik app on mobile to offload the media files to your phone.
Fusion Studio does not work with BigSur. So, I must take other way to stech the files of Gopro Fusion. Without Phone app.
Is there any other way?
@hokkaidofishfilms, apologies for the inconvenience. Please see https://gopro.com/en/us/news/fusion-end-of-life for more details.
Thank you for the advice. There seems to be no way in my case. I have to choose an old pc or a new camera...