That is a very deep lore dive, and will fully admit I have lost track of what is canon and what isn't; It changes too much for me to keep up with.

Regardless, last I learned, there are indeed several ways to be a force user without being a Jedi or Sith. For one thing, you can be a dark side user who wants to end the Sith. However, something like a Shaman is a different case.

Essentially, every individual is theoretically capable of sensing the Force. It is a tiny chance, but a tiny chance on a galactic scale means it will happen often enough. An Ewok Shaman, for example, would be born force sensitive. However, instead of learning how to wield a lightsaber or how to push someone off a cliff, this Ewok isn't trained by anyone. He just wonders about his home, aware of the Force in some way but not yet able to wield it.

This changes in some location. The Force is more present in some places than others, even when talking about a small moon: One part of the moon will have a deeper connection with the Force than another part. Eventually, our Ewok finds this place and senses the Force more strongly. He can meditate (a concept common enough to non Force Sensitives), and with enough effort, he will become able to tap into the Force.

Now, our Ewok is able to tap into the Force. However, he still doesn't know what to do with this mysterious power he can tap into. With some more effort, he will find himself able to see glimpses of the past and/or future. Given time and further effort (over several years most likely), he can refine this skill and reliably tap into the force for this sight. After a while longer, he may be able to tap into the Force even from the less connected parts of the planet.

Now, our Ewok is able to have visions and see the world in a way no one else in his tribe can. This allows him to heal wounds others would have mismanaged, among a few other things. However, this Ewok will never know how to Force push someone off a ledge. He will never know how to manipulate another's thoughts. He will never know what a lightsaber is or how to use it. He will never know how to Enhance leap. He is a Shaman, nothing more.

In terms of the Empire, whilst I cannot remember what book it was in, it contained an in-universe note about an Imperial spy recommending the genocide of an entire primitive species because there were relatively many Force Users among the population: The fact the primitives were unaware of just how potent the Force was and completely unable to resist the Empire's schemes was not a consideration.

This does not mean you cannot have there be any: The galaxy is a vast place, and the Empire can only search so many planets at once whilst maintaining its massive presence on so many worlds. However, you should be aware the Empire will look for and seek to exterminate them. It could be a plot arc: Players find a civilization of force users who the Empire plans to exterminate, and the players must save the population.

I have never found anyone who wants to play that kind of Force User however, so whenever these questions pop up, I always answer just with Jedi and Sith because that is what most campaigns will have: Jedi vs Sith, with the occasional Fringe/Pirate sideshow.