For some reason, Samsung disabled assigning custom ringtones for contacts on their Galaxy S21 series smartphones. Maybe someday Samsung will fix it with an update, but until then I found a simple solution. If you are having this issue, take the following steps:
1. Go into your phone settings, scroll down and then select "Apps"
2. Scroll down and then select "Contacts"
3. Select "Permissions"
4. Select "Storage"
5. Enable "Allow access to media only"
You'll now have the option to select custom ringtones for all of your contacts:
1. Open your phone app, select "Contacts" and then the contact name
2. Select the info icon on the right
3. Select "Edit" on the bottom
4. Scroll to the bottom and select "View more"
5. Scroll to the bottom and select "Ringtone"
6. Select the ringtone, and then click "Save" on the bottom right
Continue to select custom ringtones for your contacts as needed.
