Since the root user should have access to everything, I don’t know why you would have permission denied error. My only idea would be that your docker client was somehow connected to the wrong Docker daemon which ran as a non-root suer and that had no access to the file descriptor. But I cannot imagine how that could work as even Docker contexts belong to specific users so your root user would not see a Rootless Docker context of another user.
There was another issue where I saw some of your error messages, but not the “permission denied”
and for me, it looks different, bt Docker Desktop starts it’s own virtual machine so if that doesn’t rely on your actual host Operating System’s configuration.
I also never tried Ubuntu 25.10, so I don’t know if that handles anything differently. If you try to install Docker in your virtual machine again and you get the same error, you could report it in GitHub · Where software is built
EDIT:
Is your host a virtual machine? If it is, How did you create that?