[Moto X4 Questions & Answers] Silently:
The firmware file PAYTON_OPW27.57-40_subsidy-DEFAULT_regulatory-DEFAULT_CFC.xml.zip that can acquired from this thread can be decompiled to find the strings:

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BUILD REQUEST INFO:

SW Version: payton-user 8.0.0 OPW27.57-40 52 release-keysM660_7036.16.01.69R

MBM Version: MBM-3.0-uefi-dfccc3a-171216

Modem Version: M660_7036.16.01.69R

FSG Version: FSG-660-01.86

Build Fingerprint: motorola/payton/payton:8.0.0/OPW27.57-40/52:user/release-keys

VERSION INFO FOUND UNDER 'ABOUT PHONE' SCREEN:

System Version: 27.31.52.payton.retail.en.US

Model Number: moto x4

Android Version: 8.0.0

Baseband Version: M660_7036.16.01.69R

Build Id: OPW27.57-40

SW Display Build ID: OPW27.2

Build Date: Sat Dec 16 07:06:03 CST 2017

OTHER MISC VERSION INFO:

Subsidy Lock Config: slcf_rev_d_default_v1.0.nvm

Regulatory Info (eLabel): regulatory_info_default.png

Blur Version: Blur_Version.27.31.52.payton.retail.en.US

Version when read from CPV: payton-user 8.0.0 OPW27.57-40 52 release-keys

AB Update Enabled: True

Full Treble Enabled: False

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And if you perform the command fastboot getvar all on your XT1900-5 you'll see the following:

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E:\>fastboot getvar all

(bootloader) kernel: uefi

(bootloader) version-bootloader: MBM-3.0-uefi-641a15b-171216

(bootloader) product: payton

(bootloader) board: payton

(bootloader) secure: yes

(bootloader) hwrev: P4

(bootloader) radio: EMEA

(bootloader) storage-type: eMMC

(bootloader) emmc: 32GB SAMSUNG DD68MB RV=08 PV=02 FV=0000000000000002

(bootloader) ufs: N/A

(bootloader) ram: 3GB SAMSUNG LP4x DIE=12Gb M5=01 M6=06 M7=00 M8=0E

(bootloader) cpu: SDM630 1.0 (6)

(bootloader) serialno: ---

(bootloader) cid: 0x0032

(bootloader) channelid: 0x40

(bootloader) uid: B871E81F

(bootloader) securestate: oem_locked

(bootloader) verity-state: enforcing (0)

(bootloader) iswarrantyvoid: no

(bootloader) max-download-size: 536870912

(bootloader) reason: Volume down key pressed

(bootloader) imei: ---

(bootloader) meid:

(bootloader) date: 09-16-2017

(bootloader) sku: XT1900-5

(bootloader) carrier_sku:

(bootloader) battid: ---

(bootloader) battery-voltage: 4284

(bootloader) iccid:

(bootloader) cust_md5:

(bootloader) max-sparse-size: 268435456

(bootloader) ro.build.fingerprint[0]: motorola/payton/payton:8.0.0/OPW27

(bootloader) ro.build.fingerprint[1]: .57-40/52:user/release-keys

(bootloader) poweroffalarm: 0

(bootloader) ro.build.version.full[0]: Blur_Version.27.31.52.payton.reta

(bootloader) ro.build.version.full[1]: il.en.US

(bootloader) ro.build.version.qcom: <not found>

(bootloader) version-baseband: M660_7036.16.01.69R PAYTON_EMEA_CUST

(bootloader) kernel.version[0]: Linux version 4.4.78-perf-ge3f7ffe (huds

(bootloader) kernel.version[1]: oncm@ilclbld67) (gcc version 4.9.x 20150

(bootloader) kernel.version[2]: 123 (prerelease) (GCC) ) #1 SMP PREEMPT

(bootloader) kernel.version[3]: Sat Dec 16 07:34:49 CST 2017

(bootloader) git:abl: MBM-3.0-uefi-641a15b-171216

(bootloader) git:xbl: MBM-3.0-uefi-dfccc3a-171216

(bootloader) git:pmic: MBM-3.0-uefi-dfccc3a-171216

(bootloader) git:rpm: MBM-3.0-uefi-245b046-171216

(bootloader) git:tz: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:hyp: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:devcfg: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:cmnlib: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:cmnlib64: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:keymaster: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:prov: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) git:storsec: MBM-3.0-uefi-eee7f2d-dirty-171216

(bootloader) qe: "qe 0/0"

(bootloader) frp-state: no protection (77)

(bootloader) ro.carrier: reteu

(bootloader) current-slot: _a

(bootloader) running-bl-slot: _a/_a

(bootloader) running-boot-lun: 0

(bootloader) slot-suffixes: _a,_b

(bootloader) slot-count: 2

(bootloader) slot-successful:_a: yes

(bootloader) slot-successful:_b: yes

(bootloader) slot-unbootable:_a: no

(bootloader) slot-unbootable:_b: yes

(bootloader) slot-retry-count:_a: 6

(bootloader) slot-retry-count:_b: 6

all: listed above

finished. total time: 0.124s

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So it seems the XT1900-5 runs a "US" firmware?