Using Macrodroid as discussed here, I was able to set up 2 macros--one ringtone for contacts and a different ringtone for non-contacts. This was done setting the macros as follows.
Macro 1 Trigger: Call incoming (Any contact), Action: Ringtone configure (ringtone for contact)
Macro 2 Trigger: Call incoming (Non Contact), Action: Ringtone configure (ringtone for non-contacts)
However, it does not appear to be functioning as I expected. At first, which ring tone was used appeared to be somewhat random, but I believe what is happening is the following:
When someone calls, whatever the last ring tone that was set is what is used. Then the ring tone is changed based on whether the person is a contact or non-contact. The following call then uses whatever ring tone the previous call set.
So, for example, if call #1 is from a contact, call #2 will use the contact ringtone regardless of whether call #2 is from a contact or non-contact.
Any Macrodroid users have any ideas?