I think there is yet another path: hyper specialization in one ludicrously specific niche no one else cares about or has good reason for not getting into.
If you spend 10k hours perfecting something no one else even thought of trying, chances are you'll be the best in the world at it.
Yeah, YouTube for instance is filled with examples of this, some of which become major success stories on the platform. In the gaming world alone, I can already think of people like pannenkoek2012 and Stryder7x, whose entire careers are basically built on glitches in Super Mario 64 and Paper Mario respectively.
And many outside that too. From medieval weaponry to chicken shop reviews, the internet has a fair people who make a living off all kinds of very specific subjects that most people wouldn't even think about.
Because generally, no competition means no demand, so while it might be satisfying to be best in the world at something, an obscure skill might not translate into financial success.
In the world of signal processing there are a lot of technical areas that are super important/lucrative but few people have expertise in them. Often it takes not only technical competence but years of experience.
To make this example even more specific, maybe you are good at writing fast decoding algorithms for new telecom standards.
There is also a lot of now low-hanging fruit in compressed sensing for the mathletes/computer people who know what that's about.
Edit: Actually, just learn math if you're looking to get ahead and have an advantage over many people. This advice doesn't make for the best blogpost or YouTube video but it's effective.
If the field you're in has a million people, then split the field into a million pieces (actually this is probably too conservative, maybe go with 100k or even 10k) and pick one to become best at.
Since the field is currently successfully employing a million people there must be that many profitable pieces if you slice it correctly.
If you spend 10k hours perfecting something no one else even thought of trying, chances are you'll be the best in the world at it.