Does Deepin use OSTree + OverlayFS? /usr is mounted read-only and I cannot write to /usr/bin

Hello,

I am using Deepin OS and I am trying to copy a file into /usr/bin, but I cannot do it even as root.

The file manager shows this error:

You do not have permission to operate file/folder! /usr/bin

I checked the permissions and it does not seem to be a normal permission issue.