[OnePlus 6 Questions & Answers] Septfox:
There was some mildly bizarre information flying around about Verizon in here...

You can take non-Verizon devices onto their network, as long as the phone supports CDMA or standard VoLTE from the outset; it can be anywhere from "mildly bothersome" to "an utter pain in the ass" to get CDMA working on a phone that doesn't have it out of the factory due to the changes in the radio and in Android needed, and VoLTE is a case-by-case thing.

Verizon has no network whitelist. They haven't since they started disallowing manual activations. The only reason your device would be disallowed on the network is because the IMEI has been globally blacklisted.

They have an activation whitelist. If your OEM hasn't paid their no doubt extortionate fees, they don't whitelist the device's IMEI range. In this case, trying to call them up to activate your SIM card - because that's what they're doing, the IMEI check is just intended to try and catch "unauthorized" BYOP users - will cause the service rep to tell you that the device is uncertified, doesn't support Verizon's network, or whatever other bull**** they've been paid minimum wage to spout at you.

This doesn't mean you're SOL, all you need to do is activate your SIM card in a Verizon device and swap it into your actual phone, and your phone will work to the best of its ability.

Band 13 is Verizon's long-range/rural band, if you never travel far from a city, don't worry too much about it. If you have no CDMA support, though, you may want to shop for it to ensure reliable VoLTE.

Lack of voice after putting an activated SIM in might be due to misconfigured VoLTE, since in theory it should "just work" as long as you have VoLTE activated on your account and a steady LTE signal.

Finally, while Verizon is the primary CDMA hanger-on in the US (maybe even the only one by now), they're not the authority on its use; most OEMs just don't bother paying the FCC extra fees to certify the bands because they can't directly recoup the cost unless they go on to pay Verizon even more fees for whitelisting activation --- and in that case Verizon will insist on a locked-down Verizon variant of the phone.

The Axon 7, for example, has full CDMA support. Because they (presumably) refused to play nicely with Verizon, they were given the middle finger, and can't be directly activated on Verizon. The phone works perfectly fine if you pop in a pre-activated SIM.

Verizon has been blatantly anti-competition and anti-consumer since the outset, have always gone out of their way to actively work against the enthusiast community, and have only gotten worse in all those respects in recent years. Don't mourn the passing of Verizon CDMA, welcome the rollout of band 71 to replace its rural coverage. That aside, I'm not saying to switch to T-Mobile specifically, but for god's sake switch to anything other than Verizon; everyone's continuing to try and improve their coverage, T-Mobile is just the one that's currently aiming specifically at rural areas.

If you have a beef with T-Mobile in particular, try one of their MVNOs. MVNOs are a delightfully impersonal experience, or at least that's how it's always been for me via PagePlus and Tracfone.

Let Verizon die, as it needs to.