What if I were a a horse-drawn carriage driver and the car industry was relegating my career into niche theme parks? If I don't want to be in that niche anymore (and I don't!), then logically, I should learn how to drive a car and become a driver.
I am just making the observation that the vast majority of available openings that can even remotely fit me (ie. not any sort of frontend) are backend, with a distant runner up of infra. If that is the reality, then I need to meet it.
It's not that I'm against niches. I like the suggestion in the other post to go into infosec. I consider that a niche too but at least most companies would need it. Very few companies make operating systems. I feel that I shouldn't have gone this direction in the first place and this struggle to find a job is a wakeup call to change.
My post already outlines my willingness to learn/retrain to fit a new reality. I'm asking for advice to make such a transition, not really looking to being told to keep doing what I've done when it clearly isn't a very portable area of expertise.