You have methods that amount to making yourself an online job, or an offline job with a lot of online communication (independent software contractor, commission artist, author, sex worker, online course teacher, Etsy knit hat manufacturer, etc.).

You also have various flavors of capitalism, which may not count, as you did say “legitimate”. But if you already have ten million dollars, you can spend lots of time researching stocks and evaluating pitches for businesses and maybe get a better return than you would otherwise, all online.

And then you have merchanting, wholesaling, or furniture-flipping type approaches: buy stuff online, refurbish it or repackage it in smaller quantities, translate all its documentation correctly, vouch for its quality and fitness for purpose, take nice photos of it, market it, sell it, deliver it, and support it.