Unity3D URP - How do I approach creating Fog of War for 3D top-down stealth game?

What I try to achieve is a fog of war system for 3d top-down stealth game. I have searched the Internet and it seems that behavior I want to achieve can be done by using secondary camera that is rendering its output to a render texture. Then render texture is applied to a plane which sits above a map with a masking shader. I was following this video: https://www.youtube.com/watch?v=PNAvNeOTnSE however my project is using URP in Unity and the Clear Flags on camera settings is missing. So basically after each rendering loop render texture gets cleared and drawn again which makes impossible to "save" areas that already have been revealed by the player.

Maybe this can be done using another technique? I would like to have fog of war that covers entire rooms with black opaque plane and reveals them upon entering them but remains cleared once visited. However visited areas should be gray once left and enemies should be hidden from the player when not in line of sight. Something like in this video: https://youtu.be/jrK_Uvwwk9I?t=1247

I would really appreciate if someone pointed my in right direction.