[Fire HD 8 and HD 10 General] bibikalka:
HD8 2018 6.3.1.5 (and 6.3.1.4) issues

HD8 2018 OS continues to present never ending issues (seems like a poorly supported product compared to the earlier Fires ...)

I flashed 6.3.1.5 (6.3.1.4) on top of 6.3.1.2 via TWRP (+Magisk/systemless Xposed), and, ended up with a weird WiFi crashloop that took a few tries to understand. Essentially, the moment it connects to a WiFi network, it reboots. If I set WiFi to off, it's stable (have to do it quick before it connects after a reboot!). If I disable Xposed module, it's stable. Neither Xposed 89.3 or 90beta work correctly.

On 6.3.1.2 Xposed worked more or less OK.

I tried to downgrade back to OS 6.3.1.2 or 6.3.0.1, but apparently the settings are not compatible once you load 6.3.1.4 on it. It never reaches the launcher, and keeps sitting at Fire screen. I could not even boot 6.3.1.2 or 6.3.0.1 without Magisk. Doing a factory reset was not in my plan yet. So I had to go to 6.3.1.4 again where it booted fine. I now run 6.3.1.4 with Xposed disabled.

Anybody has 6.3.1.4 with Xposed & WiFi working properly out there? I wonder if this is also a similar issue with Fire 7 2019 (mustang) - [MENTION=4914529]Michajin[/MENTION]

HD10 2017 40.6.5.0_user_650601220 issues

Well, what do you know ... I finally took the plunge to do the unlock and install TWRP on my Kingoroot rooted HD10 2017 (thanks [MENTION=7104332]k4y0z[/MENTION] !). I backed up all the apps via Titanium Backup, and then backed up the internal sdcard via Total Commander to a zip, which later nicely restores things back with the proper timestamps (yay!). It's very difficult to restore timestamps, but Total Commander with root can do it.

In my optimism, after getting TWRP, I immediately installed the latest FireOS, 40.6.5.0_user_650601220, with Magisk, and Xposed installed into system (xposed-v89-sdk22-arm64.zip). And, just like HD8 2018, the moment I activated Xposed modules, the tablet started rebooting when WiFi was on. If I managed to hit WiFi off button before it did so, it seemed stable. So both HD10 2017 and HD8 2018 appear to have the same Xposed bug in the latest FireOS versions!!! I wonder if it's related to the fix of MTK-SU issue.

I also ran into Google Play & battery drain issues. Tired of several attempts of troubleshooting, I actually ended up backtracking all the way to 40.6.2.6_user_626533320, which is the version I started with. Once Google Play went south after my 1st restore, I could not fix it over multiple tries, and I had to do a Factory reset again and restore apps via Titanium Backup a bit more carefully, starting with the latest versions of Google Play apps without data (rather than just all at once). Now everything appears to be working as before, with TWRP, and the same old FireOS version that I already had :)

The battery drain issue was an interesting one, apparently, Vanced Youtube helper app, microg_YouTube_Vanced_0.2.6.17455, creates a lot of battery drain via needless Wakelocks, which can be fixed by running the following commands:

adb shell
su
pm disable com.mgoogle.android.gms/org.microg.gms.people.ContactSyncService

P.S. A week ago I unlocked HD8 2017 (OS version 50.6.3.6_user_636558520), and successfully cloned HD8 2016 to this 2017 via TiBa & Total Commander. That attempt went without a glitch, and that's why I thought I could also do HD10 in no time, but HD10 gave me all kinds of issues.