Face down sleep mode Revvl 6 Pro

It definitely sounds like a proximity sensor thing. The proximity sensor is mainly known for turning the screen dark when you are on a call to prevent pushing buttons with your face. They are also used to turn off the screen when the phone is set down or put in a pocket to prevent other buttons from being pushed. There isn't a direct way to turn it off in settings because is not really recommended to do so, but a google search would get you some steps to do that. 

The only other setting that I think could affect your screen turning off when you set it down is the screen lock. Do you have a lock on your phone? Have you tried turning it off to see if the screen goes dark when set down?

ok so you might google how to boot the phone into safe mode..this shuts down all 3rd party apps just to make sure a rogue app and the update arent battling each other in the background..if the problem is sitll there then you will probably need to perform a factory reset..just make sure to back up the phone prior to doing this..im not seeing a onslaught of posts about this with this phone so it might be a fluke deal with yours. something might not have fully loaded right or it might have held onto a file that should have been dumped when the update pushed through…

cant shut down the sensors..even if you could every time you put the phone to your ear all you would be doing is dialing numbers with the side of your face the whole convo lol

And I want the sensor to not do anything, even if it gets covered 

OS update 

i just said above..if it ends up being something like that you’ll have to trim it up a bit or something so the sensor isnt blocked..again this is only a guess still. gotta troubleshoot to narrow it down..did this just up and start happening out of the blue? after downloading a new app? after a OS update?

Even if there is a sensor that turns the screen off when it comes close to my ear, what I want to know is how to stop it from doing that. 

no idea then..i know my V60 will randomly stop showing on screen notifications here and there and i have to click the power button twice to get it to turn the screen back on but its a pretty random issue on my end.

do you by chance have a screen protector or case on your phone? remove the case if you have one, restart the phone then put it face down and retest..wonder if its going to be some weird one where the case or screen protector is slightly covering the sensor and giving it false readings?

Sadly, it's neither of those 

https://www.t-mobile.com/support/tutorials/device/t-mobile/revvl-6-pro-5g

Auto screen lock?

Screen time out?

no clue..i would think it would be in something like settings-display or something about the time out of the screen. might even look under power/battery settings in case its a sleep/wake setting in there.