. . .
That site gave you a download link, which you used:
https://download.opensuse.org/repositories/home:/dliw/15.4/noarch/python3-of...
Do you see the word "repositories"?
And do you see the word "home"?
Well, that's the download link from some home repo, named "dliw".
Thanks for the explanation. And now I know as well. Yet, I find no mention of how to contact the author. Be that as it may. There one finds:python-imaplib2-3.6-lp154.7.1.src.rpm Which sadly does not matching the version of python used by offlineimap (not offlineimap3) that I am currently able to compile. While it may be possible a usable version of imaplib2 is tucked away in there, the KEY errors seem insurmountable for me at the moment, solutions not yielding to my non AI enhanced search engine skills. That said, if people want feedback to authors or maintainers on issues encountered, they ought to make it relatively easy for harried hackers to have at it.