There are other ways but Harry is now in the culture ocannot allow to establish himself as an unobtrusive presence as if he were still a working royal because he wants another kind of work and it's directly linked to his being visible.
It doesn't seem to me as if he has any definite idea of what "work" he's going to do/wanted to do. I know there were stories that well before they left royal life they were talking about deals, to US companies.. but according to H himself they didn't go for the deal with Netflix till they lost their security.
I honestly wonder if Harry understands about work, and realizes that even if you are already reasonably rich, it takes time and commitment to make really massive amounts of money. You need to be thinking about it, working on it, committed all the time to finding new ways of making the money.. and He just doesn't' really understand that.
I keep thinking of a skit in Blackadder, where there is a character who is an upper class Frenchman who has come to England to get away from the revolution. Blackadder asks him if he wants to make some money and he says "No!!!! I want other people to make the money and give it to me." I think that H thinks that somehow, other people will make the money and he'll just somehow get it...
Edward (Wessex) did set up businesses making documentaries on royal history and they didn't do that well.. because he wasn't all that smart and I dont think those sorts of docs bring in MUCH money... but he did at least try to make money by providing SOMETHING to sell that the public might buy. Harry doesn't seem to even have an idea what he might sell to the public other than his personal life... (OK there's a possible documentary on Invictus but its only ONE idea and it isn't about something that is going to make shedloads of money).