Fairphone 4
shop.fairphone.com
shop.fairphone.com
US carriers generally use 8 bands of 5G: n2, 5, 12, 41, 66, and 71, as well as mmWave bands n260 (39GHz) and n261 (28GHz). They also use 15 bands of 4G: B2, 4, 5, 12, 13, 14, 17, 20, 25, 26, 29, 30, 41, 66, and 71. They vary by carrier, and bands 5, 12, 66, and 71 overlap between 4G/5G support, see [1] and [2] for more details.
Resource [3] has a nice quick lookup table for many common phones, for example the Pixel 4a 5G supports 6 or 7 (depending on whether you want mmWave or not) of 8 5G bands and 15 of 15 4G bands. For another example, see [4]; for a couple years I used a Motorola One Zoom phone which I loved for its cameras, battery life, OLED display, Android One rootable OS, storage/headphone jack, and other properties as a device...but it had atrocious coverage. Fortunately, it supported T Mobile's most common bands of 2, 4, and 12, which were present at my home and work, but at quite a few places (usually more remote) I'd have zero signal and my wife would have excellent signal. It also supported 4G bands 1, 3, 7, 8, 17, 28, 38, and 40, but only saw a tower that served those bands when I traveled out of the country for work, which was unfortunately limited to a single trip due to Covid hitting shortly after I bought the phone.
The Fairphone 3/3+ supports 6 of 15 US 4G bands: 2, 4, 5, 13, 20, and 26 [5]. The Fairphone 4 supports 7 of 15 4G bands: 2, 4, 5, 12, 20, 41, and 71, and 3 of 8 5G bands: 5, 41, and 71 per [6]. It's not a bad device, similar to my Moto Zoom it has many other bands that are mostly used overseas, but domestically it will suffer. Fortunately for me, it dropped band 13 (little used by T-Mobile in my area) for the essential band 12, which represents some 25% of deployments in my area. Unfortunately, it lacks 1700 MHz band 66, which is about 15% of deployments, and which my wife has declared to be a requirement of my next phone.
I'm currently comparing the Fairphone 4 (3/8 5G bands and 7/15 4G bands) with Librem 5 (0/8 5G bands and 5/15 4G bands), Pinephone (0/8 and 7/15), Sony Xperia 10 II with Sailfish OS (0/8 and 11/15), Moto One 5G Ace (3/8 and 15/15), Nokia 8.3 5G One (5/8 and 10/15), Pixel 4a 5G (6/8 and 15/15), and upcoming Pixel 6 (expected 8/8 and 15/15). Also evaluating a variety of LineageOS devices. But it's really hard to cut Gsuite's all-seeing eye out of my digital life when domestic telecom coverage is so spotty and weird.
[1]: https://www.phonearena.com/news/Cheat-sheet-which-4G-LTE-ban...
[2]: https://www.phonearena.com/news/Cheat-sheet-which-4G-LTE-ban...
[3]: https://www.kimovil.com/en/frequency-checker/US/google-pixel...
[4]: https://www.kimovil.com/en/frequency-checker/US/motorola-one...
[5]: https://www.kimovil.com/en/frequency-checker/US/fairphone-3