Is it worth porting this module to Drupal 8+, or should we focus on getting this fixed in core?
We no longer need to worry about a last-changed timestamp, as this was fixed in #2074229: Add changed time tracking to taxonomy terms. So all we would need to do is add a creation timestamp. (Initially, I was thinking we could just look at the timestamp on the first revision now that taxonomy terms are revisionable, but it could have been deleted so we can't rely on that.)
Here are the related core issues:
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