Ultimately I didn't miss anything, but I started by trying to do the least possible.
And you're right, it's nonsense that we have to do anything other than Click "update".
Samsung Wallet requires Android 9 or greater to be available for a device.
Your device should be running Android 10 (One UI V2.5), so you should be fine.
Did you try the suggestions above?
- ie: Clearing Cache & Data for the app?
- Clear Cache from Recovery?
- Could also Clear Cache & Data for the Galaxy Store & Reboot.