We also have this problem but why do we suddenly need to allow this on our computers? The purpose of using the admin console to build install packages for our team (Adobe creative cloud) is to avoid this kind of problems. Everything should be put into the installation package that we build. I can't find any information about this being changed over time so that we suddenly must allow sideloading in Windows 10? Fun fact, for some of our users it was enough to "deactivate" the licens and the "re-join" them to the team but for alot of our users that isn't enough.
We need more information to find the cause of the issue like this error is coming when updating the creative cloud or installing a package on the machine, or when signing in to the creative cloud application. It would be really helpful if you could share the screenshot of the prompt.
This is still an issue. We don't allow our users to do the updates themself. This is disabled in the package but somehow Creative Cloud Desktop still want to do the updates but of course it fails but instead our users can't launch their program at all such as Photoshop for example.