As of this moment (August 1st, 2022), Julia version 1.7.3 is the latest stable release, and Julia 1.6.7 is the latest long-term support release. Most applications involving production code should be using either version 1.6 or 1.7 right now depending on the requirements for stability and support.
There is a Julia 1.8-rc3 (release candidate 3) available right now. The 1.8 beta and release candidates are meant exactly for the purpose of testing. The Julia 1.8 code was branched several months ago in February 2022. This includes package and library integration. That is we are actively seeking feedback to see if that version is compatible with currently applications. Once released Julia 1.8 will become the new stable release and support for Julia 1.7 will eventually end. Support for Julia 1.6 will continue until the next long-term support release.
The nightly releases are unstable. They represent the bleeding edge of development. Changes integrated in a day to day basis may break code. These are meant as development previews only in order to catch potential issues early. This code will likely be eventually released as Julia 1.9, although a Julia 1.9 branch has not yet been created. Some of these changes may eventually get backported to the long-term support release and the latest stable release.
Most of us should be using Julia 1.7 or maybe Julia 1.6 at the moment, while those of us doing development should be testing Julia 1.8. Some of us that need long term compatibility should use Julia 1.6.
If your requirements are that you want Julia to keep working with a certain library over a long period of time, I highly suggest depending on the long-term support release branch, currently Julia 1.6. That is the only branch where we are trying not to break things while providing maintenance (e.g. patches, security updates) over a long period of time. Support for Julia 1.7 will end eventually after Julia 1.8 is released.
In this specific case, I see that SLICOT_jll was introduced in January 2022 with compatibility starting at Julia 1.7, so I understand that Julia 1.6 compatibility is not an option at the moment.
Continuous integration is the automated system to catch these issues. It seems that system is working in that we are aware of a version 1.8 incompatibility before Julia 1.8 has been released.
While some processes are automated, I’m not sure if anything around here is “automatic”. We do not have a highly proficient AI system writing Julia for us at this time. The main “automatic” mechanism we have to do not break things is the long-term release by simply not adding new features that may break things to the 1.6 branch.
In this specific case of SLICOT_jll, @giordano recommended a fix similar to #4770 as you noted. However, there is only one Mosè Giordano. If you would like help putting together this fix, I recommend creating a post specifically about that.
In this case, it seems that you are also involved upstream, which is very helpful. This would allow us to coordinate a patch release, SLICOT patch release version 5.8.1 , that is compatible with Julia 1.8.