[Fire TV General] bibikalka:
I got the new 4k Firestick, and put it through the paces a bit (XDA style). I was not able to block the stick from updating on the very first run by throttling the WiFi connection speed (despite quite a bit of effort). Anyway, after it updated and came up, I was able to set up MoreLocale to add a non-supported language (Russian), and SmartYouTube, exactly as per instructions here:

https://xdaforums.com/fire-tv/general/fire-stick2-run-avoiding-otas-youtube-t3718556

I could not disable the OTA updates using the old commands.

For ADB, the network route works fine (adb connect 192.168.1.XX). I was also able to power the stick from a PC, and by updating device ID in the old MTK driver, the stick became ADB visible from the PC. Unfortunately, Kingoroot did not work :(

The stick appears to be very snappy, faster than Gen2. The android version is 7.1.2, so it's a major step up from 5.1.1 for Gen2. The Fire OS version is 6.2.3.2. Amazon really slowed down updates for its misc tablets, I suspect they are busy working on moving everything to 7.1.2

Here is the build.prop file from those who are interested.

# begin build properties
# autogenerated by buildinfo.sh
ro.build.id=NS6232
ro.build.display.id=NS6232
ro.build.version.incremental=0001443165316
ro.build.version.sdk=25
ro.build.version.preview_sdk=0
ro.build.version.codename=REL
ro.build.version.all_codenames=REL
ro.build.version.release=7.1.2
ro.build.version.security_patch=2018-07-01
ro.build.version.base_os=NHG47K
ro.build.date=Wed Nov 7 18:06:26 UTC 2018
ro.build.date.utc=1541613986
ro.build.type=user
ro.build.user=build
ro.build.host=i3-ri-14-use1a-b-63
ro.build.tags=amz-p,release-keys
ro.build.flavor=mantis-user
ro.product.model=AFTMM
ro.product.brand=Amazon
ro.product.name=mantis
ro.product.device=mantis
ro.product.board=mantis
# ro.product.cpu.abi and ro.product.cpu.abi2 are obsolete,
# use ro.product.cpu.abilist instead.
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.cpu.abilist=armeabi-v7a,armeabi
ro.product.cpu.abilist32=armeabi-v7a,armeabi
ro.product.cpu.abilist64=
ro.product.manufacturer=Amazon
ro.wifi.channels=
ro.board.platform=mt8695
# ro.build.product is obsolete; use ro.product.device
ro.build.product=mantis
# Do not try to parse description, fingerprint, or thumbprint
ro.build.description=mantis-user 6.0 NS6232 1268 amz-p,release-keys
ro.build.fingerprint=Amazon/mantis:6.0/NS6232/1268/N:user/amz-p,release-keys
ro.build.thumbprint=6.0/NS6232/1268/N:user/amz-p,release-keys
ro.build.characteristics=tv
# end build properties
#
# from device/amazon/mantis/system.prop
#
#
# system.prop for generic sdk
#

rild.libpath=mtk-ril.so
rild.libargs=-d /dev/ttyC0

# MTK, Infinity, 20090720 {
wifi.interface=wlan0
# MTK, Infinity, 20090720 }

# MTK, mtk03034, 20101210 {
ro.mediatek.wlan.wsc=1
# MTK, mtk03034 20101210}
# MTK, mtk03034, 20110318 {
ro.mediatek.wlan.p2p=1
# MTK, mtk03034 20110318}

# MTK, mtk03034, 20101213 {
mediatek.wlan.ctia=0
# MTK, mtk03034 20101213}

#
wifi.tethering.interface=ap0
#

# wifi rssi->bar thresholds
persist.wifi.rssi.thresholds=-85,-80,-73,-69

ro.opengles.version=196610

wifi.direct.interface=p2p0
dalvik.vm.heapgrowthlimit=128m
dalvik.vm.heapsize=256m

# USB MTP WHQL
ro.sys.usb.mtp.whql.enable=0

# Power off opt in IPO
sys.ipo.pwrdncap=2

ro.sys.usb.storage.type=mtp

# USB BICR function
ro.sys.usb.bicr=no

# USB Charge only function
ro.sys.usb.charging.only=yes

# audio
ro.camera.sound.forced=0
ro.audio.silent=0
ro.mtk_box_audio_support=1
ro.zygote.preload.enable=0

ro.kernel.zio=38,108,105,16
#ro.kernel.qemu=1
#ro.kernel.qemu.gles=0
ro.boot.selinux=disable

ro.sf.lcd_density=320

# disable ipo for development
sys.ipo.disable=1

#for sw gpu alloc
#ro.hardware.gralloc=mt8695.sw
ro.mtk_alps_box_support=1
# for ethernet extention
ro.mtk_alps_ethernet_ext=1

#add for 8695box cec device type
ro.hdmi.device_type=4

#add for svp
ro.mtk_sec_video_path_support=1

ro.nrdp.modelgroup=FIRETVSTICK2018
ro.nrdp.validation=ninja_5.1

# Android OpenGL renderer configuration
# Configure as if we're a 1080p 1GB device
# (we can consider Mantis Tank + .5GB for 4k)
ro.hwui.texture_cache_size=48.0
ro.hwui.texture_cache_flushrate=0.4
ro.hwui.layer_cache_size=32.0
ro.hwui.drop_shadow_cache_size=4.0
ro.hwui.path_cache_size=16.0
ro.hwui.r_buffer_cache_size=4.0
ro.hwui.text_small_cache_height=512

dalvik.vm.heapmaxfree=2m

# max size(kb) of FDR whiltelist, 512MB
ro.recovery.wl.maxstore=524288

#Support storage visible to apps
persist.fw.force_adoptable=true

#Dynamic warming service
persist.sys.ps.favapps_limit=2

#dma continuous mode devices
persist.dolby.dma.devices.cm=1152

# enable offload mode for video
audio.offload.video=true
#set min duration as 1 sec for video in offload
audio.offload.min.duration.secs=1

# limit buffers for streaming apps
ro.trim.buffers=1

#
# ADDITIONAL_BUILD_PROPERTIES
#
ro.build.lab126.buildtype=Nightly
ro.build.lab126.project=mantis_fireos_ship_6232
ro.build.lab126.build=1268
ro.build.version.fireos=6.0
ro.product.package_name=com.amazon.mantis.android.os
ro.build.configuration=tv
ro.build.version.serial=1268
ro.config.notification_sound=OnTheHunt.ogg
ro.config.alarm_alert=Alarm_Classic.ogg
ro.fireos.resources=framework/fireos-res/fireos-res.apk
config.disable_networktime=true
dalvik.vm.skpheapgrowthlimit=20m
dalvik.vm.skpheapmaxfree=512k
dalvik.vm.skpheapminfree=128k
dalvik.vm.skpheapstartsize=2m
dalvik.vm.skpheaptargetutil=0.95
ro.hdmi.wake_on_hotplug=false
dalvik.vm.heapgrowthlimit=192m
dalvik.vm.heapsize=384m
ro.logd.kernel=true
ro.mediatek.chip_ver=S01
ro.mediatek.platform=MT8695
ro.telephony.sim.count=2
persist.radio.default.sim=0
persist.radio.multisim.config=ss
wifi.interface=wlan0
service.adb.tcp.port=5555
wifi.tethering.interface=ap0
ro.mtk_sec_video_path_support=1
ro.mtk_key_manager_kb_path=1
ril.specific.sm_cause=0
ril.external.md=0
ro.btstack=blueangel
ro.sf.hwrotation=0
drm.service.enabled=true
ro.mtk_in_house_tee_support=true
fmradio.driver.enable=0
ril.first.md=1
ril.flightmode.poweroffMD=0
ril.telephony.mode=0
dalvik.vm.mtk-stack-trace-file=/data/anr/mtk_traces.txt
mediatek.wlan.chip=MT7668
mediatek.wlan.module.postfix=_mt7668
ril.radiooff.poweroffMD=0
ro.mtk_protocol1_rat_config=no
ro.mediatek.version.branch=alps-mp-n2.mp12.tc6sp
ro.mediatek.version.release=alps-mp-n2.mp12
ro.mediatek.version.sdk=4
ro.num_md_protocol=2
ro.mtk_bt_support=1
ro.mtk_audio_tuning_tool_ver=V2.2
ro.mtk_wlan_support=1
ro.mtk_search_db_support=1
ro.have_aacencode_feature=1
ro.mtk_widevine_drm_l1_support=1
ro.mtk_hdmi_support=1
ro.mtk_emmc_support=1
ro.telephony.default_network=0,0
ro.mtk_shared_sdcard=1
ro.mtk_pq_support=2
ro.mtk_pq_color_mode=1
ro.mtk_world_phone_policy=0
ro.mtk_perfservice_support=1
ro.mtk_hdmi_hdcp_support=1
ro.mtk_internal_hdmi_support=1
ro.mtk_key_manager_support=1
ro.mtk_cam_mfb_support=3
ro.mtk_external_sim_only_slots=0
ro.sim_me_lock_mode=0
ro.mtk_dual_mic_support=0
ro.mtk_is_tablet=0
wfd.dummy.enable=1
wfd.iframesize.level=0
ro.mediatek.project.path=device/amazon/mantis
ro.com.android.mobiledata=true
persist.radio.mobile.data=0,0
persist.meta.dumpdata=0
persist.radio.mtk_ps2_rat=G
persist.log.tag.RIL-DATA=D
ro.boot.opt_using_default=1
mtk.vdec.waitkeyframeforplay=1
ro.sys.sdcardfs=1
ro.media.maxmem=500000000
ro.dpframework.not_support_yv12=1
debug.log.thermal_qa.enable=n
persist.sys.hdmi.keep_awake=false
dalvik.vm.dex2oat-threads=3
ro.product.config.type=AKPGW064GI9HE
persist.sys.recovery.batt_level=25
persist.sys.ota.verified=unverified
persist.sys.ota.last_verified=none
persist.sys.dalvik.vm.lib.2=libart.so
dalvik.vm.isa.arm.variant=cortex-a7
dalvik.vm.isa.arm.features=default
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt
ro.build.version.number=0001443165316
ro.build.mktg.fireos=Fire OS 6.2.3.2
ro.build.version.name=Fire OS 6.2.3.2 (NS6232/1268)
ro.expect.recovery_id=0x9fcb0ab2f1f9483f404aeab2ca8929ee416780a5000000000000000000000000