Seeking Advice on Pre-Signup Event Tracking in Mixpanel

Hey everyone, I need one help regarding Mixpanel - product analytics. To avoid blockers, we have added all events post signup at backend. Things are looking good until we want to add events pre signup as well. We are thinking of adding them at backend only and triggering them via APIs but then pre signup we don’t have their userID as distinct keys. If we use random UUID as distinct ID then funnel will act funny. Thinking of adding IP address simply as identifier but it poses security risk and also the fact that I have to pass IP address in all API requests. Refraining from using identify function of mixpanel as it suffers from same blockage issue. Does anyone know some good solution on how to plan this? Thanks in advance!