[Verizon Motorola Droid Turbo Android Development] ChazzMatt:
No, I wasn't saying it's a kernel issue, I'm just pointing out not only does a non-Verizon phone (ZTE Axon 7) now suddenly have Verizon VoLTE with stock ZTE Nougat, but so does ZTE Axon 7 LOS 14.1 custom ROM. NEITHER had it with stock Marshmallow or CM13. LOS 14.1 is not a stock-based, debloated ROM like CF's ROM is here for the Droid Turbo. There's no secret why CF ROM has VoLTE -- he just didn't remove whatever makes it work when debloating it. :p

But ZTE Axon 7 is a different story. The only thing ZTE stock Marshmallow and ZTE LOS 14.1 share is modem and some kernel code. As far as I know, everything else is different. Yet, Verizon VoLTE now works on both.

Basically that's what's already been done, or was done. Back 2 years ago in March 2015 [MENTION=2228410]Skrilax_CZ[/MENTION], our CM dev, took the Motorola KitKat 4.4.4 kernel and "ported" it to be used in CM12 (Lollipop 5.0.2). Motorola had not yet released Lollipop kernel sources yet. He then took the Lollipop kernel when it finally came out and used it in CM12.1 (Lollipop 5.1) and later also for CM13 (Marshmallow) until Motorola released Marshmallow kernel sources. When Motorola did that, he then ported the Motorola Marshmallow kernel to work in Marshmallow CM13... Here's one post.

July 23, 2016

When the Droid Turbo XT1254 was bootloader unlocked in November 2015, [MENTION=2228410]Skrilax_CZ[/MENTION] had to modify some things to make the Droid Turbo totally compatible with the Quark ROMs. I'm fairly sure [MENTION=2228410]Skrilax_CZ[/MENTION] kept the kernel as "stock" as possible while having to make it compatible for CM ROMs, but you would have to ask him or now [MENTION=5747496]bhb27[/MENTION].

Now, during all this time, [MENTION=5747496]bhb27[/MENTION] started working on an advanced custom kernel that had more tweaks, more governors, more I/O schedulers, etc. [MENTION=2228410]Skrilax_CZ[/MENTION] was just porting the Motorola Quark kernel to work with CM ROM. All other ROM makers (even "AOSP") have to use the Quark CM kernel. But [MENTION=5747496]bhb27[/MENTION] was focusing on the kernel to try to improve performance, battery tweaks, etc.

Since [MENTION=2228410]Skrilax_CZ[/MENTION] has taken a break (I hope he's OK), [MENTION=5747496]bhb27[/MENTION] has taken on the CM (now LOS) "stock" kernel work in addition to his separate BHB27 custom Quark kernel. The last time [MENTION=2228410]Skrilax_CZ[/MENTION] posted on XDA was October 2016, but I'm happy to see he's still logging in and reading stuff. His profile shows last activity was a few days ago in April 2017. I am very thankful for all the work he did for our Quarks.

[MENTION=5747496]bhb27[/MENTION] is very busy, and has kept up both the "stock" kernel work and his own name brand kernel. Exactly what the difference is between Motorola stock kernel in stock firmware and the CM/LOS tree "stock" kernel, you would have to ask an expert like [MENTION=5747496]bhb27[/MENTION] or [MENTION=2228410]Skrilax_CZ[/MENTION] (who created that tree).

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[MENTION=2640499]koftheworld[/MENTION] pointed out the ZTE Axon 7 may be an anomaly, maybe Verizon has changed policies to make BYOP easier or something. Who knows?

So, he astutely pointed out the XT1250 may hold the key. When and why does it get Verizon VoLTE? It's a Quark. Is it because it's on some Verizon whitelist? (it's one of the phones sold by Verizon's rural CDMA/LTE roaming partners -- LRA or LTE in Rural America) Is it because it has the same FCC ID as the XT1254 Droid Turbo? Does it get Verizon VoLTE when on stock 5.0.2? Or do you have to flash Verizon firmware, either stock or CF debloated ROM? If we can figure out when/how the XT1250 gets Verizon VoLTE, then perhaps that can be incorporated into custom ROMs so the Droid Turbo XT1254 can get Verizon VoLTE.