[Android Q&A, Help & Troubleshooting] Waelyn:
Background​

Hey folks,

I followed this general process for rooting an Onyx Boox TabX E-Reader tablet:

(TL;DR got the boot.img from Onyx, and patched and rooted it with Magisk)

Android version: 11

Magisk version: 26.4

The tablet is now rooted, I was able to install LinuxDeploy and get debian up and running (and run Jetbrains Gateway compiled for arm linux for remote code development which was the goal)

Problem​

So that's all awesome. However android is eating some of my critical keyboard shortcuts (Ctrl+Space most critically, which Android eats and turns into a "change language" command on the Android OS side) so they don't get forwarded through the VNC to the IDE. (Why Android would you not make this behavior user configurable by default!?!?!). My actual "Physical Keyboard" settings in the Settings app has basically nothing (Shortcut Reminder On/Off, Enable "Wake up the device with the keyboard" On/Off, Display virtual keyboard On/Off).

I found where the physical keyboard shortcuts for my keyboard are stored (for me it's /system/usr/keychars/Vendor_18d1_Product_5018.kcm). But I CANNOT FOR THE LIFE OF ME EDIT THAT FILE.

So concretely: No method I've tried has allowed me to mount "/" as R/W

If there's a way to remove all of the stupid android default physical keyboard hotkeys without that, great, but from what I've seen I don't think there is.

What I've Tried​

adb root gives me "adbd cannot run as root in production builds"

I got this project compiling with some tweaks: https://github.com/tiann/adb_root (only patched adb_root I could find that works with android 11)

Got the zip, tried to install it with magisk, nothing happened. Don't know much about magisk modules admittedly so this was kind of a hail mary anyway. I suspect that it might've been compile for x86 (I compiled it on my laptop) despite having the aarch64 toolchain. I'm going to try compiling it under my debian running on linuxdeploy on the tablet itself but I don't have high hopes.

I downloaded both the "Root Explorer" app and the "Material Files" app, and despite granting them root permissions in Magisk neither of them could mount the file system as root either. So even if I get the patched ADB loaded I doubt it would work anyway but maybe I'm wrong. Even local apps with root permissions appear to be unable to remount the filesystem

Tried the solution to modify the boot.img that PokeRekoP mentions here: https://xdaforums.com/t/fully-rooting-onyx-boox-poke3-e-reader.4307453/

But with my limited knowledge of magisk/Android I couldn't find how to make the flag change mentioned. I extracted the image, dtb, and cpio files and saw some fsmgr_flags in the fstab files but didn't see the specific file mentioned in that post, or any "verified" flags being used for that matter. This approach appears the most promising to me but with my limited knowledge of magiskboot I can't quite figure out how to make it work

I've been poking into ways to modify the contents of a boot.img file, from what I can tell that's basically the purpose of magiskboot but I haven't found how to actually get at the files with it...

So I'm loosing my mind and any help would be appreciated 😅