PNG's a no show

Got the message that docker version not supported
Installed docker-ce, now is my forum gone?

After running the latest Discourse update a few days ago, clicking the the download icon opens .txt files in a browser instead of downloading them, yet no Discourse settings were changed. Yet now .png files are displaying properly. So a deeper problem is occuring.

I implemented the Discourse/Docker periodic manual full update instructions and watched error messages.

All updates .launcher rebuild app I received an error message that docker 17.05 is not supported, minimum required is 17.06.02. Ubuntu has changed the package name from docker-engine to docker-ce. Is it safe to install docker-ce, as this won’t be an upgrade? Because of the docker version preventing app rebuild, my forum is down. :frowning: What do?