It's not like the fundamentals of your request haven't been discussed for as long as software had a lifetime. Occasionally this results in enterprise products. You are free to run your machines openSUSE machines in any way you like. But I am also free to point out that it is a bad decision to depend on an OBS devel project repositories that are known to not have an archive, where did remove them repeatedly, and said so usually long in advance.
IMHO your argument, to force users to upgrade, whenever a new release of OpenSuSE comes out, does a big disservice to users who simply can't keep up.
Nobody is forcing you to upgrade or do anything. But that does not imply that anyone else has to do anything for you. Your system is still working fine. Just hw-info is not available for a new installation, a change you attempted to do. As for keeping up, may I point out to the comfortable release cadence, and the 8 months that have passed since 15.4 is EOL and the one year that has passed since the successor release 15.5 is available.
Now I got to worry about even older OpenSuSE systems I support, will I be even able to upgrade them when intermediate repositories are being abandon, or not archived?
You, should not rely on development repository builds to remain available in perpetuity. hw-probe is part of openSUSE Leap 15.5 and 15.6 and is maintained there. You should report any bugs that prevent you from upgrading.
So what am I suppose to do when I can't upgrade?
You could engage a local expert, possibly in a LUG. And of course our fabulous community that will get you to a maintained release. Andreas