Yes, a segmented bar could preserve transfer-source information and round-by-round gains, which probably captures most of the useful information of a Sankey in a much simpler UI.
However, the Sankey’s unique advantage is showing the complete path of individual vote flows through multiple candidates, and imho also looks more fun 
But for Sankey you’d have to allow for either:
- adding an additional dependency, or
- building a Sankey in house (which might not be so bad now we are in the age of Coding Agents)
I think the bar graph is a good intermediate step if you are worried about the complexity of a complete Sankey presentation.
In any case you are going to have to modify the API for either presentation.