@lpr you are obviously right, but one could argue that this question has been written with much more effort, formatting and most of all references.

@lpr thanks for pointing this out.

It's indeed pretty similar to the point 1 of my request.

Sorry for the dupe: as the author of that request wrote the unusual 'µG' form instead of the much more common 'microG' - it happened to never pop-up in searches during the last ~1 year I've been using it.

Regarding the request there are still a couple of differences making fusion of the two thread a bit more complex:

• it dates back from 2016, it dates back from the era of Jolla 1 phone and Android 4.2 Jelly Bean running inside Myriad's modified Java-VM Aliendalvik. Quite a few things have changed nowadays with Sailfish X on Xperia XA2 with AOSP 8.1 Oreo running inside a LXC (Linux container).
• Back then the signature spoofing was relatively new and without much infrastructure. That post argues for an always integrated signature spoofing (and points that having this feature always-on is a big security risk).
• A 2017 update then points to solutions used in MicroG for LineageOS (which limits signature spoofing to /system privileged apps)
• Nowadays we have AOSP 8.1 Oreo which allows (since 6.0 Marshmallow) much finer-grained permissions control. Nowadays, Signature Spoofing is a permission that can be granted to specific apps, and modern microG has a special settings UI to control it. It's definitely NOT always-on (and can be turned on on-demand only for the GmsCore framework that actually needs the spoofing, and nothing else).
• Also, there's the whole system.img thing: nowadays, Android aren't 'just' Java(-like) bytecodes ran inside a Java(-like) VM (Dalvik), they are a full blown binary native system (ART - Android Runtime). And thus Android application compatibility layer isn't just a modified Java(-like) VM, but a full blown self-contained AOSP image. On Sailfish X this image is read-only SquashFS and there is no easy straight-forward way to write inside /system. The whole restrict spoofing to priviledged apps is a dead end.

(Also this is just half of my request, then there's the whole point 2, which is an entire extra chapter. Apparently, given the report of gamers playing Pokemon Go on MicroG+Aliendalvik, that wasn't a problem back then, but is now)

How do you remove all traces of the Google Play apps

If you want to manually uninstall, MicroG has a wiki explaining what to manually delete

(OpenGapps pico version if installed by the instructions),

If you have installed by the instructions you will have a file called system.img.orig in the directory were you've run the script. This is your original untouched image, you can start a new using this one.

NOTE: usually upgrading Sailfish OS overwrites the image with the latest version. So if you happen to have installed openGapps before, and then upgraded to 3.1.0.11 Seitseminen afterward, your image is latest clean.

How do you get a clean /opt/alien/system.img in case you lost your original one

General "howto" discover which package a files comes from:

$ rpm -qf /opt/alien/system.img 
aliendalvik-8.1.0.53.57-1.17.1.jolla.armv7hl

Thus you need to force re-installation of the file. So if you use zypper:

zypper install -f aliendalvik

(Sorry I'm not very fluent in pkcon, but perhaps something like: pkcon install --allow-reinstall aliendalvik ?)

The MicroG FAQ talks mostly of the "apps" that in this case were squashfsed into the system.img. They are taken care of by just going back to using the original system.img.

But the Play Store app and the Play Services hidden "app" are installed to somewhere else in the file system in the Opengapps setup process, and those apps and their other installed data needs to be purged. Maybe the apps can be removed from Aptoide, but...

And you probably need to remove your Google Account from the Android Settings in order to "log out" from Google within the Android layer.

And when doing a full reinstallation of Android Support, you quite likely need to remove all the Android app icons and whatelse in specific Sailfish folders. I wrecked my whole OS by doing it wrong (=only halfway through) a couple of months back.

for where the additional stuff outside of /system is stored, it's mostly in the android_storage and /home/.android.

See the twohowtos written by kostas12ldb (except you don't want to copy them, but purge them instead).

Specifically for the upgrades to Google Services, you can also uninstall them with some Adb commands (see microG wikis).

To get an Android shell, you need to type on Sailfish as toot (do devel-su):

lxc-attach -n aliendalvik /system/bin/sh

Alternatively, whatever package manager you used to install the upgrade (Google Play Store? Aptoid Store?) can remove the upgrades with an easy GUI : it's the same process like uninstalling applications, except the button says "downgrade" instead of "remove" for APKs that are also present in system.

That's the damnest thing really: I can find all my other Android apps in /home/.android/data/app/ folder, but com.android.vending (=Play Store) isn't there. Even madder, the .desktop file in /usr/share/applications/ that handles the launcher icon points to that exact folder.

After you first time execute the Opengapps script on your system.img and then restart Android Support after that, you will automatically go through the initialization that installs Play Store. Apparently the apk is installed to some weird Android place, but non-devel-sued File Browser isn't authorized to look into all folders.

So... is the com.android.vending apk actually inside the patched system.img, and in the "Android/data/app/" folder there, and it's the only Opengapps App showing on your launcher because it's the only one of those apps that get a launcher icon installed (in the initialization phase I guess)?

So in other words, there are two Android/data/ folders in the system: one in the /home/ folder and another squashfsed inside the system.img, and the Android Support layer sees and deals with both of them simultaneously (?).

So when reverting to the vanilla system.img I probably also have to purge manually /home/.android/data/data/com.android.vending/ which is the /home side folder for the downloads and init files and stuff that obviously can't be in the read only system.img.