LineageOS + Open Gapps: remove Gapps, dirty migration to "LineageOS for microG" fails

I've got a Motorola Moto G4. Bootloader unlocked, TWRP installed, LineageOS installed, Open Gapps installed, non-rooted. Been using it for about a year. I want to try [LineageOS for microG](https://lineage.microg.org/) . I want to keep my current data/apps (including some end-user Google apps like their PDF viewer) as much as possible and migrate to microG, removing only the "core" Google stuff a user doesn't generally care about directly that will be replaced by microG. So, I'm following the dirty install process. --- I have none of the listed apps installed. I have tried removing Open Gapps, but it doesn't seem to work. Using the aroma installer to choose settings until the config at the end is "Include" with *no* apps listed, some Google apps are still installed (notably, the Play Store) after rebooting. The Open Gapps installer process also mentions removing existing/obsolete apps for only a short time, then moves to the next step "installing Gapps" which takes a long time. This seems to contradict the settings I gave it, namely to leave none installed, but is consistent with the fact that they don't seem to get uninstalled. I have also flashed https://github.com/CHEF-KOCH/Remove-Gapps to try to get rid of them, but some Gapps (like the Play Store) still survive. --- After any combination of attempts to follow the instructions and remove the Gapps, I flash the key migration zip followed by the lineage-microG.zip for my device (athene). I also make sure to wipe the Dalvik and cache partitions before rebooting. After all this, every time I reboot, my system is almost *exactly* like it was before I did anything: Google services installed (though the Play Store does not actually work, it's still there), the microG settings app is not installed, etc. A few things are broken (some notifications of apps crashing) but overall nothing noteworthy has happened. I've resorted to even wiping /system before a migration attempt, but even this achieves nothing. --- I got a partial success once by manually going through /system/app, /system/priv-app, and /data/app and removing anything that looked Google-y, then performing the migration. Upon rebooting, the microG settings app was present and the self-check section looked like it should look on a clean install, but the Play Store was still present. I don't know to what extent this migration was a success. I'm not familiar with the Android/Google ecosystem's insides and app politics, just the userland, so when I'm manually going around deleting files, I have little knowledge of what I'm doing, so I don't consider this attempt a success. --- Now that all the info has been laid out, could someone please help me cleanly perform the migration to lineage-microG, without excessive butchering of my system or leaving things that should not be left? Why does the dirty install procedure laid out by the lineage-microG team fail? Why do the Gapps removal tools fail? What exactly is necessary to correctly and cleanly migrate lineage to lineage-microG?