OK - I can answer some of my questions now; maps, Greenify and Sophos do all work IF they get installed AFTER microG. So uninstalling and reinstalling them helps.
FINAL RESULT
I learned from this thread that:
- a logcat app is very useful (a “must have”)
- I prefer microG much over opengapps due to ease of installation (however it still incoporates quite a number of steps (see ✏ How to install any app on FP Open OS (for beginners and experts) step 5.5):
- add the microG repository (from website) to F-Droid
- Install the latest microG Services Core
- Install the latest microG Services Framework Proxy
- Install the latest FakeStore
- Install at least one UnifiedNlp backend - I use LocalGSMBackend and NominatimGeocoderBackend
- Install an app for signature spoofing - I use FakeGApps Xposed module
- patch needed to make unified register: change microG Services Core and microG Services Framework Proxy to be system apps (instead of user apps) - do this manually or use an app like Link2SD
- Open microG Settings
- grant/give/allow all rights and permissions asked for
- Do the “Self-Check”
- Ensure that all points are checked. If one of the points is not checked, read its description.
- Tap on “UnifiedNlp Settings” and set up the Nlp Backends you installed in a previous point
- Reboot
- you might need to enable location stuff in andorid phone settings
- Open microG Settings > Self-check again. Now all points should be checked. If so then you succeeded!
- some apps need to be installed AFTER microG in order to work (un- and reinstall them)
- the Swell Pro App works with microG and maps
- the EZ-GUI Ground Station App not (actually it complains not beeing compatible with the device - but it’s the OS, as it worked with Fairphone OS in the past on the exactly same device before the update)
1 of 2 apps do work now (the more important one, as it cannot be replaced or substituted by anything else I know).
Thanks to all for your support!