stroly-json from https://stroly.com/ to GeoJSON

convert.py

import json

with open("landmark1 (1).json", "r", encoding="utf8") as fr:
    landmarks = json.load(fr)["landmarks"]

with open("landmark.geojson", "w", encoding="utf8") as fw:
    fw.write("""{
"type": "FeatureCollection",
"name": "points",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
"features": [""")
    id_num = 0
    for item in landmarks:
        fw.write("{ \"type\": \"Feature\", \"properties\": { \"id\": "+str(id_num)+", \"name\": \""+(item["langs"][0]["name"] if len(item["langs"]) >= 1 else "")+"\" }, \"geometry\": { \"type\": \"Point\", \"coordinates\": ["+str(item["lng"])+", "+str(item["lat"])+"]}}")
        id_num += 1
        if id_num == len(landmarks):
            fw.write("\n")
        else:
            fw.write(",\n")
    fw.write("]}")