Now that I just realised - according to the C:\Program Files\Little Navmap\little_navmap_db\README.txt - that the little_navmap_navigraph.sqlite is actually placed in a well-known location, namely:
C:\Users\[User]\AppData\Roaming\ABarthel\little_navmap_db\little_navmap_navigraph.sqlite
I am heavily inspired to make use of it as well 
select *
from airport a
where a.name like '%Same%'
3794 1 HTSE Same AFR HT [...] 37.7000007629395 -4.08333349227905
Ah! Even the Same Airstrip is available - the same Same Airstrip that we initially get 30 times with the SubscribeToFacilities results (and the only 30 results that we get with RequestFacilitiesList), with the same lat / lon coordinates.
I will probably go for a “mixture” like:
- If Little Navmap DB is installed: use it (skip the following points)
- SubscribeToFacilities, store the received airports in an unsorted hashmap (key: ICAO, value: airport data) and at the end of the flight see whether we get some meaningful results out of this (that is, iterate over the hashmap and compare the start / end coordinate of the flight with the coordinates of the airports: if within a given threshold distance → that’s the airport we flew from/to)
- Try again with
GPS WP NEXT IDandGPS WP PREV IDand see whether we get values here (last time I tried with SimvarWatcher to get those as “string variables” I received empty values, even though I had setup a simple FROM / TO flight plan on the FS 2020 world map - maybe the aircraft needs to have a “GPS navigation device” built in in order to get actual values here? Or “GPS / NAV / autopilot” needs to be engaged?)
But jeez! All this in order to get two simple ICAO code values, of the start and end airports (if started / landed) of the flight…