Only country from some reverse adresses

I now see that this is more a result of wheter this is a city, village, town etc.

% curl -s "https://nominatim.openstreetmap.org/reverse?format=json&accept-language=en&lat=52.475697&lon=13.36397" | jq .address
{
  "amenity": "S-Bhf. Südkreuz / Hildegard-Knef-Platz",
  "road": "Hildegard-Knef-Platz",
  "suburb": "Sch?neberg",
  "borough": "Tempelhof-Sch?neberg",
  "city": "Berlin",
  "ISO3166-2-lvl4": "DE-BE",
  "postcode": "10829",
  "country": "Germany",
  "country_code": "de"
}
% curl -s "https://nominatim.openstreetmap.org/reverse?format=json&accept-language=en&lat=52.475697&lon=13.36397" | jq .display_name 
"S-Bhf. Südkreuz / Hildegard-Knef-Platz, Hildegard-Knef-Platz, Sch?neberg, Tempelhof-Sch?neberg, Berlin, 10829, Germany"

while

% curl -s "https://nominatim.openstreetmap.org/reverse?format=json&accept-language=en&lat=62.576187&lon=11.388272" | jq .address
{
  "house_number": "25",
  "road": "Bergmannsgata",
  "quarter": "Sm?hagan",
  "farm": "?sen",
  "town": "R?ros",
  "municipality": "R?ros",
  "county": "Tr?ndelag",
  "ISO3166-2-lvl4": "NO-50",
  "postcode": "7374",
  "country": "Norway",
  "country_code": "no"
}
% curl -s "https://nominatim.openstreetmap.org/reverse?format=json&accept-language=en&lat=62.576187&lon=11.388272" | jq .display_name   
"25, Bergmannsgata, Sm?hagan, ?sen, R?ros, Tr?ndelag, 7374, Norway"

https://github.com/ymichel/Geolocation-Plugin/blob/d031ed553610f5b8b416c5a0b22241224e17a0fa/geolocation.map-provider-osm.php#L144

The addresses are currently combined out of the attributes city, suburb and country only.
If I see your second request, it might make sense to also have town, municipality and country as alternative. Did you discover also more possible outcomes?

BTW: I already provided the option from above in 1.9.6

Looking at https://wiki.openstreetmap.org/wiki/Key:place the list might contain

• city_block
• neighbourhood
• quarter
• suburb
• borough
• city

• allotments
• farm
• isolated_dwelling
• hamlet
• village
• town

(allotments and farm might not be that useful)

• municipality
• subdistrictcounty
• district
• province
• region
• state
• country

In some cases there is also the name that might be useful. E.g.:

$ curl -s "https://nominatim.openstreetmap.org/reverse?format=json&lat=48.85830&lon=2.29487&zoom=18" | jq 
{
  "place_id": 115316935,
  "licence": "Data ? OpenStreetMap contributors, ODbL 1.0. https://osm.org/copyright",
  "osm_type": "way",
  "osm_id": 5013364,
  "lat": "48.8582599",
  "lon": "2.2945006358633115",
  "class": "tourism",
  "type": "attraction",
  "place_rank": 30,
  "importance": 0.5868325701744196,
  "addresstype": "tourism",
  "name": "Tour Eiffel",
  "display_name": "Tour Eiffel, 5, Avenue Anatole France, Quartier du Gros-Caillou, Paris 7e Arrondissement, Paris, ?le-de-France, France métropolitaine, 75007, France",
  "address": {
    "tourism": "Tour Eiffel",
    "house_number": "5",
    "road": "Avenue Anatole France",
    "city_block": "Quartier du Gros-Caillou",
    "suburb": "Paris 7e Arrondissement",
    "city_district": "Paris",
    "city": "Paris",
    "ISO3166-2-lvl6": "FR-75C",
    "state": "?le-de-France",
    "ISO3166-2-lvl4": "FR-IDF",
    "region": "France métropolitaine",
    "postcode": "75007",
    "country": "France",
    "country_code": "fr"
  },
  "boundingbox": [
    "48.8574753",
    "48.8590453",
    "2.2933119",
    "2.2956897"
  ]
}