Last November I recorded how important Dataverse metadata fields were mapped to RIS tags and what happens when the RIS files are imported into different reference managers (and when different reference managers pull the metadata from html metatags): https://docs.google.com/spreadsheets/d/1ZW5-KmKk5dJWZAD12m7xc1i11xtEY_4vCvTVK72bG38/edit#gid=0
Maybe that'll be helpful? I saw that when we download an RIS file from the landing page of a tabular file, the UNF for the file is in the RIS. (But like you saw, Janet, the dataset UNF isn't in the RIS file we get from the dataset page.)
I also saw that the dataset description and PID also don't show up when importing the RIS into Zotero, which I thought was much more of a problem.
It's awesome that you're tackling this, Sebastian!