movies Websites to sign up to test screening?

I hope I posted it in the right thread this time 😅
So I've watched a video from this filmmaker
and I thought it could be a very cool experience to come to a test screening.
So I found websites for major studios, obviously.
Warner Bros:
Disney: It's not available for the public which is fair enough to me.

But! I couldn't find a website that gathers all the film studios. Because I would really like to go to test screening from more independent filmmaker.
So, any recommendations?
I'll be very happy to hear them

Ps: I know because of Covid 19 you can't go to the movie theater but I just wanna know it so that when they open, I know where to go. :)