How to read data from an unreadable drive formatted by a GoPro?
The solution was to use a Windows computer with an SD card socket to read the card and transfer the files.

Before that, I tried the following methods mentioned in the answers and the comments. The YUTU PRO smartphone application could transfer small files and not large ones (more details below). The retailer had no idea about the problem or solutions. I did not try @BaconDuctTape's MiniTool recommendation as Windows had solved the problem.

For the future, I will format any card with MS-DOS (FAT).

more details on YUTU PRO app

I followed the directions on the user manual. I was lucky that one file was small enough
  for the phone's available space; unlucky that the second transferred but
  failed to show and lingered somewhere (a common ghost file problem). The app showed two videos with duration 00:00 when they have
  06:49. The app alone was taking 3.3 GB and has no menu option to delete its data. Rebooting the phone clears the
YUTUPRO ghost data (hint from here).

Then I deleted all photos from the
phone, downloaded small files (around 3 minutes of footage) one by one from the app to the phone, transferred to the computer,
deleted the file on the Photos app, went to Albums &gt; Recently deleted to delete
permanently, and started again.

For files at the maximum of 6:46, which showed as 0:00, the app was able to play them by streaming, but not
to transfer them. The app showed "Downloading, Please Waiting ..." (sic, see below) for several hours. So I went for the Windows solution.