Taking a break from industry and becoming an unpaid research assistant (or atleast getting involved in reserach at a school)
In my field (though different from yours), 3-6 months is not nearly enough time for a novice to approach a research project.

Student volunteers (undergraduates, who may also get credit for the work so not entirely "volunteer") may take on projects of this duration, but there is little expectation that they accomplish anything concrete - they take more time to train than their research output is worth.

That said, a university has a mission to educate students, and that trade-off is okay for students - it's a service to the next generation of researchers, to make sure students get exposure to what research is like. If you aren't a student, it's harder to make a case that the time should be spent with you rather than those interested, enrolled students. Yes, you may be interested in maybe switching to a research career, but you're not nearly as invested in that exploration as someone who is enrolled in a degree program.

Additionally, there are the legal issues with what defines an employee as in the answer you already linked.

There are more issues as well involving privacy, data security, intellectual property, etc: universities have policies and agreements in place to address these concerns for both students and staff; you can't really sneak a volunteer in without going through those same processes, so it isn't quite as simple as just "showing up".

Lastly, just a bit of a caution:


  an enthusiastic individual who has a decent academics and willing to give up 6 figures


does not seem to me nearly as impressive as you make it sound, especially when you've made it clear you are secure enough financially to go unpaid for a bit. Any university is full of currently enrolled students who have financial and life difficulties and yet are working towards a degree already without the security that you've built for yourself. They are enrolled and earning meager salary despite having those responsibilities like children, sick parents, and family members in dangerous situations elsewhere in the world. It's fine to be proud of what you've done for yourself so far, but I'd be very cautious in thinking that it positions you above others in any way.