In French, the plural they is the masculine ils for mixed gender groups, and only the feminine elles for groups that are exclusively feminine. On is a singular gender neutral form of they often used in situations with unknown gender.
I would use on for singular and ils for plural when talking about a non-binary person because that seems the most reasonable application of the language as I understand it.
However as a non-native speaker I would defer to whatever native speakers do. Can't say I know what the established best practice is.
Stop blaming the voters for kamala's bad decisions.
she threw her campaign when her campaign chose to abandon the very vocal block of anti-genocide voters who had enough votes to swing the election.
if your campaign can only succeed if several millions of people to change their minds suddenly, you ran a losing campaign from the beginning.