Comment 12 for bug 1892915

@vorlon it is in the graphic which shows up in the GUI surrounding the checkbox to enable -proposed
here: https://wiki.ubuntu.com/Testing/EnableProposed?action=AttachFile&do=get&target=devoptions_1604.png

Thank you @knox for the clarification. This was largely my fault for doing a 's/focal/groovy/g' in my sources.list.

I can't speak to whether the GUI source selection interface allows one to add -proposed to the primary sources.list when the devel series is running though.

Is there a way to tell apt that packages which have a dependency upon libffi7 should absolutely not be mixed with packages which depend upon libffi8 because there is a breaking change? (I imagine there is no automated way to notice that hey data structures have changed between library versions.)

And for the benefit of users in the future who accidentally hit this sort of issue, can anyone recommend a best practices way to downgrade all packages which are for instance built against libffi8ubuntu1?