Hi Jack,
That's answered at the top of your second link -- there are no unsupported/supported file formats: "Harvard Dataverse Repository supports any data format regardless of file extension."
There are file formats for which specific functionality is available: Tabular ingest (see the link you posted, though I don't believe the version numbers of the software are current -- e.g. RData files from R v4.x are supported.
Previewers are more complicated and I don't think there's a full list anywhere -- there's also a fair amount of configuration that goes into this (e.g. Harvard Dataverse is configured to preview .do files and .R files as text files -- which they are -- but doesn't do that for .py files, though they're in the exact same category).
Al best,
Sebastian