currently, I'm not aware of any collections planned for CentOS 8;
modularity/AppStream is the prefferred way forward.
Since RedHat does not support collections on RHEL 8, it would take a community
effort to update and maintain the scaffolding in CentOS 8. Given that
these days I think I'm the only semi-active member of the SCLo SIG,
I would not hold my breath.
Of course, If you are willing to try and put in the work,
try joining the SIG  and start figuring out what exactly is needed.
So Red Hat does and does not seem to support collections on RHEL-8. The CentOS Stream of 8 ships with two software collections gcc-toolset-9 and gcc-toolset-10 which are newer gcc collections than the base one. However it doesn't seem they have other tools needed to make software collections in 8 so work would be needed to update and maintain the scaffolding.
Software Engineer, Red Hat
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