Hi JitteryCoyote63

Or even better: would it be possible to have a support for HTML files as artifacts?

If you report html files as debug media they will be previewed, as long as the link is accessible.
You can check this example:
https://github.com/allegroai/trains/blob/master/examples/reporting/html_reporting.py

In the artifacts, I think html are also supported (maybe not previewed as nicely but clickable.
Regrading the s3 link, I think you are supposed to get a popup window asking for S3 credentials, but I'm not sure, I'll check with UI guys :)