It allows to take pictures with blurred background in portrait mode.
The phone was trying to connect to a 5G signal and the SIM card couldn't handle that and was causing the signal to get "stuck".
In some countries, including the UK and Australia, the S20 is the only variant with a cheaper 4G-only option.
This is a photography setting you have to choose, and these images take up to eight times the amount of storage space as a default photo, at least in my experience.
Estimated software update time is 6-10 minutes.
Click the START button, sit back and wait few minutes.