I think Beatrice and Eugenie are relatively good leads to follow here, to some degree. They both have titles and grew up as princesses and they both now have normal jobs and a few charity patronages for things they are genuinely interested in. They don’t receive funding because their charity work is seperate to the monarchy, my theory would be that Charlotte and Louis will follow a similar path.
it would make sense for their to be a plan for them to support George whilst doing their own thing. The problem that crops up is when that thing operates in contrast to the monarchy. Working for an art gallery like Eugenie? Fine. Working on tell all royal documentaries for Netflix? Not so great
ETA- you also have the funding problem. If they are doing some official work they are entitled to public money, but if they also have their own job and private income it’s a murky water. Financially at least, you really do have to be either in or out