I have the Note 20 Ultra and Object Eraser is available with the 3.1 update. The Note 20 Ultra didn't get any update for phone call background feature. Also Goodle Discovery is not available either. There are some features that haven't been passed down from S21 3.1 to Note 20.
Yes I noticed that about the Samsung Pre Installed Call Backgrounds missing. I just use my own anyway. I knew about Google Discovery being locked to the S21.