For animated GIFs it would be neat if the DC software could use a technique such as this to automatically add a play/pause button:

https://codepen.io/chriscoyier/pen/pogQJER

That Codepen sample plays such GIFs by default unless user's browser preference is set for reduced motion (see the JS in the sample), but by not setting the 'open' attribute on the details tag (line 5 of the HTML in the sample) it could always start paused.

The technique relies on having a static image containing one frame of the animated GIF, so that would need to be done server-side when an animated GIF is uploaded.

By doing a second install using Normal level security, then comparing webapp settings, I have tracked down the cause of my problem.

My install was a Minimal security one, after which I changed the settings of the /csp/sys web app and its sub-apps /csp/sys/* by clearing the Unauthenticated checkbox and setting the Password one.

But it seems that unless I do the same for the /api/interop-editors webapp I get a Rule Editor authentication page which I am unable to get past, not even by entering the credentials of the same %All-role user I logged into /csp/sys (i.e. Portal) with.

As soon as I made the change to /api/interop-editors I was able to get into the new Rule Editor, seeing only a brief flash of its authentication paged.

Here are the tweaked Minimal-security settings that work for me (i.e. authentication required to access Portal, from where I can move without challenge into the new Rule Editor):