[HTC 10 Questions & Answers] dRm42:
Hey Guys! I have the same problem as Swarai. As per datafoo's recommendation, I've read the error message :) I've found that the root cause of the problem is that from TWRP I can only mount /System as readonly, if I untick the "mount system as readonly" checkbox, it doesn't allow me to select the system partition. I can click on it, but the checkbox never gets marked. I'm on TWRP 3.0.3-0_UNOFFICIAL, as recommended in https://xdaforums.com/htc-10/development/recovery-twrp-touch-recovery-t3358139. Also tried from terminal by using "mount -o rw,remount,rw /system". No luck. also tried "/sbin/mount -t ext4 -o rw,remount /dev/block/bootdevice/by-name/system /system" and "/sbin/mount -t ext4 /dev/block/bootdevice/by-name/system /system" - both ended up with "Invalid argument", but I couldn't figure out which argument was wrong. Both are mentioned million times on XDA as an advice to mount system as rw. Not sure what I'm doing wrong.

From within the OS, root checker says root is properly installed (used SuperSu 2.79 with "KEEPFORCEENCRYPT=true"). I'm S-ON.

Because of this, I'm unable to flash Xposed-v87-sdk23-arm64.zip

Has anyone seen this before? What am I doing wrong? Can anyone please point me to the right direction?

**** EDIT ****

If anyone wanted to answer, don't bother :) I guess it's something with TWRP and I didn't want to read all the 5 million TWRP posts that are here, so chose another path. I've installed Systemless Magisk + Systemless Xposed framework instead. It works beautifully.

For those of who need step-by-step guide from Stock to rooted + Xposed:

* Unlock phone with HTCDev.com

* Flash latest TWRP. Currently the latest official is 3.2.0.7 but TWRP 3.0.3-0_UNOFFICIAL also worked for me.

* using adb, while in TWRP, run: adb shell "echo KEEPFORCEENCRYPT=true>>/data/.supersu". You can double check if all went well by running: adb shell "cat /data/.supersu". This should return KEEPFORCEENCRYPT=true.

* Flash the latest SupserSu from TWRP. At time I'm writing this it's v2.76.

* Flash UNOFFICIAL Systemless Magisk v10.2 from TWRP (https://xdaforums.com/xposed/unofficial-systemless-xposed-t3388268). I guess you can just download this from the app store, but it was middle of the night and I forgot to enable "Unknown Sources" on my phone. Therefore the apk install didn't work for me, so I flashed it.

* Turn on Settings > Security > Unknown Sources. This is what I should have done before trying to install Magisk and I could have saved myself a recovery boot :) THIS IS VERY IMPORTANT, if you don't do it, everything will look ok, but your Xposed won't install properly.

* From within Magisk, choose the version of Systemless Xposed Framework for your version of OS (MM => SDK 23). From here on it's the same as regular Xposed.

* Install Xposed Installer to manage Xposed modules. The framework won't work in itself, this is pretty much the management GUI for it: https://xdaforums.com/showthread.php?t=3034811

* Reboot and Enjoy! ;) Install the plugins you need, I only have Android N-ify to have recent double click and new notification options + NotifyClean to get rid of BoomSound notification.

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HTC 10 64GB TW

6.0.1 (1.98.709.5)