[flir]

From personal experience: Education and third sector (charities), or the companies that support them. All the universities I've ever dealt with have an ancient patchwork of backend systems, many of which are on the .NET side of the fence. Fair warning: you're not going to get fintech money in the third sector.

(Lot of people telling you your personal line in the sand is wrong, rather than just answering the damn question. "Try to change an arms manufacturer from within as a grunt programmer" is especially out-there).