Sorting stacked bar chart legend

n_n afaik, I don't think there is a way to sort the legend. May be you want to put this as an idea on ideas forum or vote if idea already exists.

You could change the order of the legend (and thereby the order of the stacked bar chart) by means of a sort-by column:

https://docs.microsoft.com/en-us/power-bi/desktop-sort-by-column

Does that do the job for you? If you really want to sort by the value, I could imagine calculating the sort-by column - but it would still be the same order for each year.