Murena Fairphone 4 has had VoLTE and VoWifi support in the USA since the end of last year.
See my post from December 20, 2022: Fairphone 4 supports 4G calling (VoLTE) in USA with /e/OS 1.6
No. Verizon is a very controlling company and will likely never allow a deGoogled phone (or Linux phone, like Librem 5 or PinePhone) on their phone network. They declined the offer by Apple to be the first carrier to support the original iPhone because Apple would not agree to pre-install Verizon apps (malware) on the iPhone. The only reason Verizon later supported the iPhone is because it was a massive success when it launched with AT&T.
Another thing to note is that the Fairphone 4 lacks support for half of the main cellular bands used by Verizon 4G LTE (B13 and B66). So it would not have a good connection to the Verizon network anyway.
It is true that the device needs to be on the AT&T authorized devices list to be able to activate a new SIM on their network, but it might be possible to use a SIM that has already been activated with an approved device. It might also be necessary to contact AT&T to have them manually approve your Fairphone 4.
As mentioned above, T-Mobile is more welcoming to new devices using their network compared to AT&T and Verizon.
Also, the Fairphone 4 supports all of the main cellular bands used by T-Mobile 4G LTE in the USA (B2, B4, B12, and B71) and supports T-Mobile Mid-band and Low-band 5G (n41 and n71). In contrast, the Fairphone 4 lacks support for one of the main cellular bands used by AT&T 4G LTE (B17) and lacks support for half of the main cellular bands used by Verizon 4G LTE (B13 and B66). Though it does support Mid-band and Low-band 5G for AT&T and Verizon (n77 and n5), T-Mobile is widely seen as the industry leader in 5G roll-out in the United States.
From Murena Fairphone 4 page:
4G supported bands | B1 / B2 / B3 / B4 / B5 / B7 / B8 / B12 / B18 / B19 / B20 / B28 / B32 / B38 / B40 / B41 / B71
5G supported bands | n1 / n3 / n5 / n7 / n8 / n20 / n28 / n38 / n41 / n71 / n77 / n78
*Main bands for USA carriers are marked in bold.
From PhoneArena page explaining 4G LTE bands:
АТ&T | B2, B4, B5, B12, B14, B17, B29, B30, B66
Verizon Wireless | B2, B4, B5, B13, B46, B48, B66
T-Mobile | B2, B4, B5, B12, B66, B71
Sprint | B25, B26, B41*Main band for each carrier is marked in bold.
*Edited to match syle used above.
From PhoneArena page explaining 5G bands:
mmWave spectrum 5G bands:
n260 band (based on 37GHz to 40GHz frequencies) — used by Verizon Wireless, AT&T, T-Mobile
n261 (27.5GHz to 28.35GHz) — used by Verizon Wireless, AT&T, T-MobileMid-band 5G spectrum:
n77 (3700MHz) — mid-band used by AT&T and Verizon
n41 (2500MHz) — used by new T-Mobile (formerly used by Sprint)Low-band 5G spectrum:
n71 (600MHz) — used extensively by T-Mobile
n5 (850MHz) — used by AT&T and Verizon
n2 (1900MHz) — used by Verizon
I’ll end this comment by saying that I am very happy this phone is finally available for sale in the USA market! To my knowledge, this is the first and only deGoogled phone that can be purchased in the USA directly from an OEM or OEM partner. This is huge! Americans without the skills, patience, or desire to deGoogle a phone themselves (most Americans) can now buy an Android phone that is free from Google malware!
Thank you to the e Foundation for making this happen!