Might have found the answer myself (and from a 2022 thread started by myself!): got the answer that buildpkg is not anymore maintained and that chrootbuild should be used instead. Can this info be added to the readme in the git project to which buildpkg belongs?
Yes - a quick forum search for buildpkg does bring up a few results with the above advice. For example:
I was just thinking along similar lines. Maybe also a message that buildpkg is deprecated in favor of chrootbuild when the buildpkg command is run (if a deprecated message isn’t already there)?