To me free will is the claimed ability to take a decision without this decision being the result of the interactions between the fundamental constituents the brain is made of or whatever makes the thought possible. — Rotorblade

I don't see how that definition works b/c any conscious decision will always be based on interactions with the unconscious that is creating the context and perceptions that conscious thought works within, which makes grounded thoughts possible. maybe you can better refine your definition in this light.

Any particle can deviate from the minimum action path, so everything has what you call primitive free will. The deviation is random — Rotorblade

not really. what you are talking about is in pure quantum states which have no action on the real world. As Feynman discovered in his QED theory, all those pure quantum random paths that deviate from the PLA cancel out to collapse only into the classical PLA path of action we observe.

So, sure, there is a possibility for any single particles that have a probability to act otherwise, ,however, they do so with such low probabilities it could take the age of the universe for it to actually happen. Hence, it effectively never happens; e.g., you will never observe photons not refracting from air to water according to the principle of least time (i.e., Snell's law).

I don't see how that definition works b/c any conscious decision will always be based on interactions with the unconscious that is creating the context and perceptions that conscious thought works within, which makes grounded thoughts possible. maybe you can better refine your definition in this light.

Maybe you want a definition by which free will is possible but you can see that even from a definition free will is not possible. Anyway my definition seems not to allow this freewill but it doesn’t say that explicitly and for some people it would not mean free will by this definition doesn’t exist. Or as you said the definition needs to be reconsidered.
My definition is actually similar to yours. You say that a free agent would be able to make the nature deviate from the principle of the least action. I said that the decision is not a result of the laws amongst them the principle of least action. So if the decision doesn’t come from the laws, it comes from the agent so the agent causes things to deviate from PLA.
If we accept the theory of evolution and we see how from simple mechanisms, lifeforms got more complex then developed a nervous system for centralized coordination then they simply got better and better it doesn’t seem any way free will would simply appear at some point in these brains. But the feeling we have about ourselves, the others and animals that they have free will is so strong.

If we accept the theory of evolution and we see how from simple mechanisms, lifeforms got more complex then developed a nervous system for centralized coordination then they simply got better and better ... — Rotorblade

they did not simply get better and better or more complex. Far more than that, in fact. They created ever more hierarchical, objectified, and disassociated layers, leading, at some point, to metacognition and qualia.

it doesn’t seem any way free will would simply appear at some point in ...these brains. But the feeling we have about ourselves, the others and animals that they have free will is so strong. — Rotorblade

exactly. Far from being a reason of no free will as you think, metacognition and qualia is the pinnacle achievement of sentience in providing sentient beings with objectified existence disassociated from the matter which it executes upon/within, thus having the property of self-determination path within any given set of constraints. So, our definitions would seem to diverge far more that you say, including b/c we end up with opposite conclusions and reasons.

In my opinion, it would be easier to approach the question of "free-will" based on the process that we make our decisions.

For the most part, we humans act based on our tendencies, which are brought about by our biological/environmental upbringing - nature and nurture. If someone likes spicy food, it's because they were raised that way. If someone finds a particular thing more aesthetically pleasing than the other, it's because the environment (media, culture, peers, education etc...) taught them to prefer that particular thing over the other.

So, where would the question of free-will be applied? I think it lies in those decisions where the options are precisely 50-50 or equal in value. And again, this is extremely rare, if you really look at it objectively. I don't even know of an experiment that would create an exact 50-50 situation since we're all always leaning (even slightly) towards one thing or another - again, based on our upbringing (nature and nurture).

This essay tries to define agency in physical terms:

Agency in Physics, by Carlo Rovelli
https://arxiv.org/pdf/2007.05300.pdf

Also worth checking the work of Jennan Ismael.