I've created a dashboard with a couple of bar graphs and two tables. Both bar graphs have drilldowns that set/unset two tokens to hide/unhide the related table. Also those tokens are used as part of the respective table search query.
Using the UI option to convert the dashboard to HTML does nothing when clicking the "Convert Dashboard" button.
Checking the logs I found that web_service.log complains about something in line 63 of drilldown.py (in the python3 path):
TypeError: a bytes-like object is required, not 'str'
That line is a call to logger.warn, passing some string parameters to %s and %d placeholders. If you remove the placeholders and the parameters, and feed logger.warn a literal string, "Convert Dashboard" now works.
I feel this is an issue with the migration to Python3 (and the change from byte strings to unicode in strings, from Python2), although I'm not sure if it lays entirely on the side of Splunk or if there's something on my server configuration that might have something to do with it.
I'd file a bug report but I don't have an active support contract.