Can I suppress ("blue-screen"?) the background of a video? I am going to record a short (approximately 5 minute) video of myself talking.

I want the background (which will be "bla" and perhaps a bit grainy, as I will probably just be using the built-in photo app on my iPad) to be "blacked out" (it will be whitish (the sliding doors of my clothes closet will be my "background")).

There is an app/web site that removes the background of still images of people (remove.bg); I want to do the same with this video (and then turn the background black, rather than leave it white, as I do with Paint's "bucket" feature after downloading the background-removed picture after using the site above).

Is this possible? Of course it is; I guess my real question is, "How can I do this using the built-in video capabilities of my iPad or via a free or inexpensive video creation/editing app"?
Well, white could get quite difficult, it would need to clearly differnce you from the white background. (Dark clothes, dark hair...)
Else I'd guess this won't give a good result.
It would be better if you hang a green/blue clothe behind you. Something like a bath towel will do it just fine enough. Make sure to hang it really tight and put some good lighting on it.