Samsung have decided to not allow the phone's gallery be synced in the Samsung Cloud unfortunately.
They are not “ dumping” Samsung Cloud as this backs up much more than just photo's stored in the phone's gallery.
Now a person can take up OneDrive if they wish.
Personally I don't use OneDrive as I find it clunky and does not sync as seamlessly as Samsung Cloud did.
So now I auto backup any picture I take to Dropbox.
I'm not signed into OneDrive anymore.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.