A lot of technical skills require access to enterprise systems to develop, or years of experience in a domain, or access to client data to learn how to handle real-world scaling issues and real-world edge cases.
Is there a well-paying in-demand technical skill that you can learn alone, remotely?
This used to be React (or Vue, in my case). You could get very good, just hacking on your own projects. And it was in demand and paid well, before the market got saturated (and before the end of the era of free money).
Can you think of a niche, highly in-demand technical skill that an average person, learning on their own, can pick up and start offering now?
Learn how to use AWS cheaply and effectively, or GCP or Azure. But probably AWS.