Since the OP was written, I contributed Ranked Choice based on Instant Run-off which closes the gap somewhat.
I’m not certain the Discourse team would like to make the Poll plugin any more complex.
I subsequently created a fork of the Poll plugin which adds a Sankey diagram for Ranked Choice. This will not be PR’ed because CDCK feel the plugin is already large enough (and that’s fair enough, it takes significant resources to maintain all this code)
If someone wants to fund the addition of Condorcet you can contact me privately to add it to the fork.