Dreadnought

Hello. Like the title says, I was wondering if there was a list, or failing that, whether anyone has personal experience with "old style" flip phones that work well with Sync 3 on a Lincoln MKZ? In my case, the version is SYNC 3.4 21194. Not looking to do anything fancy (kind of obvious I guess, since I'm using a flip phone). Just want it to link with Bluetooth, stay linked, and download contacts (and make calls). So far I have tried four phones. My oldest phone works great. Unfortunately it was 2G and no longer works with Verizon's network (or anybody else's either). Of the 4G phones I have tried, only one has worked decent in terms of Bluetooth connections (an "ETalk Kazuna") but that phone is such a dog otherwise that I'm looking to replace it. Tried a Nokia 2720 a couple years ago. It would link OK, but would disconnect from Bluetooth after I made one call, every time, thus necessitating a reconnect. Also had a "TCL Pro" that frequently would not call out and would partially freeze the SYNC display and make using unrelated voice commands impossible. Also was hit or miss in terms of downloading contacts.That phone was a real piece of trash. So.....looking for phone suggestions, or hints as to operating system, etc. on these types of phones that play nice with SYNC 3. Thank you.