Hi @Jmsc30 I would do two things.
Check the compatible list, but be aware that this list is about phones that are known to work. It really doesn't say anything about the other phones.
The other step I would do is to search the boards for a phone model that your interested in.
It sounds like I'm like you, I have a Samson SG8, with no desire to update, and haven't have a compatible issue since June of 2 or 3 years ago.
You might consider a Samsung SG8 to SG10. These are know to be very reliable and can be found at greatly reduced prices.
I personally think that as long as your phone has at least Android 7.0 it should work, I don't buy all this compatible phone list stuff as no Android I have ever owned is on the list yet they work fine. The main thing is it needs at least BT 4.0.
There are some phone models that do sync and send notifications, but are not easy to add the tracker to a Fitbit account.
For these phones, it is easier to borrow a phone to setup the tracker. Then when logging into the app on your phone, you will find that the tracker is setup.
Several other phones have quirks that are usually easy to get around, like needing power management for the Fitbit app to be disabled.
This is the reason I suggest a search, users have found these quirks and it might help in making a decision.