No longer works - latest dropbox requires libffi7 (maybe more)

From the docker logs:

Checking for latest Dropbox version...
cat: /opt/dropbox/VERSION: No such file or directory
Latest : 214.4.5217
Installed:
Dropbox is up-to-date
cat: /opt/dropbox/VERSION: No such file or directory
Starting dropboxd ()...
/opt/dropbox/dropbox-lnx.x86_64-212.3.5673/dropbox: error while loading shared libraries: libffi.so.7: cannot open shared object file: No such file or directory

Start with the Docker image setup and the Dropbox startup entry point, then compare the log's /opt/dropbox/VERSION lookup with the installed Dropbox directory. Check how the image supplies libffi and how the Dropbox version is detected. Done means the latest Dropbox starts without the libffi.so.7 error and the version checks report a valid installed version.

Written by the indexing model from the issue text.