I found a pretty decent mockumentary I'd never heard of before, The Atticus Institute:
When the US government attempts to weaponize the power of a possessed woman, they soon discover that there are forces that exist in this world that simply cannot be controlled.
Basically, it's a play on old CIA experiments with psychic stuff. The mockumentary fills in the plot, while all the scares are in surveillance footage with some handy cam stuff scattered in. So it's mockumentary exposition followed by found-footage scares...and it works pretty well. The interviews really set a creepy tone about what everything is leading to. The found footage stuff feels believable in most of the scenes, and some of the ways the "entity" messes with the researchers have a genuine creep-factor to them.
I found it pretty effective. I was always interested in what was gonna happen next, and it didn't take too long between good moments. My one complaint is that the ending didn't quite live up to the hype because it was a little too abrupt. But the actors and effects really hold it down for such a found footage movie. Ironically, the best stuff is when the entity communicates with people...the possessed woman is great, and what she says and knows about everyone else creates some GREAT moments.
Anyway, this is on Tubi and seems really slept on. It's not a Tubi Original! It's a lot better than 99% of Tubi schlock and also a fairly standout mockumentary. I liked it!