I used to be able to do this with my Samsung S9 plus but recently got the 23 plus and it won't work. Any suggestions?

The ability to have individual ringtones for each user already exists, but Chomp doesn't take the ringtones from the device's contact settings. Each contact must be set up individually in Chomp and it isn't obvious to the new user how to do so. Here is how you currently set up individualized ringtones in Chomp:
1. If you do not yet have a conversation thread with the contact of interest, text them so you do.
2. From the Conversations screen, long press on the contact of choice and press "Notifications".
3. Press "Ringtone".
4. Now you see the options that are available. Choose either "Ringtones" or "Music" for a list of the tones on your phone.
5. Select the ringtone you want. You will have to know what the ringtone sounds like based on the file name (since there does not appear to be a way to hear a sample of the sound within Chomp).

Can already be done mate.

This is possible on the stock messaging app on my Note 4 but not here? That's crazy! I need to know my wife's texts from everyone else's.