Android 11, rooted (Magisk): mount system_ext in read/write to remove Google Apps

Issue

I want to remove Google apps and services on a new Fairphone 4 (Android 11, now rooted using Magisk. No TWRP build available yet.).

To this end, I am trying to use microG. In the Prerequisites for its usage, signature spoofing and deleting files in system/priv-app are listed. For signature spoofing, I followed the XPosed solution for Android 11 and 12 listed here, i.e. using Magisk + riru + LSPosed + a FakeGApps fork. Not sure, whether or not this worked. All individual steps reported success, but the Signature Spoofing Checker says it didn't work.

Anyway, I'm definitely stuck at the second step, because I don't seem to be able to delete any files in system_ext/priv-app. I tried the solutions proposed here and here. If I try

adb shell
su
# then confirm on the phone, then
mount -o rw,remount /

I get '/dev/block/dm-0' is read-only. Similar error (with dm-1) if I try mounting /system_ext.

adb root or adb disable-verity don't work, because it's a user build: adbd cannot run as root in production builds, verity cannot be disabled/enabled - USER build.

I even tried to write a Magisk module to replace the directories in question with empty ones, by putting the following in the customize.sh:

REPLACE="
/system_ext/priv-app/GoogleFeedback
/system_ext/priv-app/GoogleOneTimeInitializer
/system_ext/priv-app/GoogleServicesFramework
/system_ext/priv-app/SetupWizard
/system/system_ext/priv-app/GoogleFeedback
/system/system_ext/priv-app/GoogleOneTimeInitializer
/system/system_ext/priv-app/GoogleServicesFramework
/system/system_ext/priv-app/SetupWizard
"

I think /system/system_ext and /system_ext are hard linked, but not sure whether that matters. After loading that module and rebooting, the contents of those folders are still the same when checking with adb shell.

Any ideas?

For adb I'm using my desktop with Ubuntu 21.10.

Solution

I asked the question simultaneously on the XDA Forums, and got a reply there.

At the stage described above (unlocked bootloader, Magisk, signature spoofing with riru + LSPosed), all that's needed is to install NanoDroid with microG as a Magisk module. Download the current NanoDroid-microG zip from here:

https://downloads.nanolx.org/NanoDroid/Stable/

either on your phone directly or transfer it to your phone, then install it as a Magisk module from storage. Voilà, GApps are removed (or at least inaccessible) and microG works. Best to then update microG, e.g. via its F-Droid repo: https://microg.org/download.html.

Answered By - RL-S