Very nice! I don't use these platforms but it's a very positive gesture. I hope someone wins it who really appreciates it.

The others phones that I know of: Xiaomi Redmi Note 9 Pro - sounds like VoLTE is working for people, but band compatibility may not be perfect. Xiaomi Poco X3 NFC - "" Various Volla - "" I've heard of people in USA using all three of these, but you really need to do your research and check with mobile providers. Brax 3 has a UT port that's coming along. Applee has been in touch with them. It seems too early to say though, which is too bad, because they have a December shipment coming along. Similarly Furiphone talked in the past of a UT port, but I haven't heard anything about it in a while. Both of those are explicitly made to work well in USA (among others). Also Fairphone 4 is supposed to have working VoLTE now? There was an ebay seller in USA who was selling Fairphone 4 new. NeverMSRP I believe. Ruben continues to work on VoLTE on the Oneplus Nord N10. Crossing fingers on that. Some people already have good results, but he's clear that it's still wonky so far.

Did you install Android 13 first, before installing UT? That step in the guide is important for all hardware to work as expected.