GeoJSON is a fundation format for Web based GIS platform
Short answer:
ESRI can't use GeoJSON
Long story:
1). Economically:
GeoJSON invented by Mapbox, not ESRI.
To prevent money flow to other company, esri natually allergic to GeoJSON.
ESRI's prefer you to use their "biological" children EsriJSON
than "stepped" son GeoJSON
2). Technically:
GeoJSON only have 1 coordinate system which is WGS1984.
EsriJSON can handle any existing coordinate system
by its spatial reference attribute WKID (well-know-id)
Step 1.
Use Arcgis Pro, here is how to export shapefile, geodatabase,layers to GEOJSON format. This is only tool that ESRI support geojson format. Others will not support geojson format.
GeoJSON unit is always degree,
a number in geojson for example 89.34
is always means 89.34 degree latitude or longitude
The number 89.34 in EsriJSON could means
Meter or US-foot or Degree
or what ever unit depends on coordinate system WKID attribute specified.
In EsriJSON, if WKID specified is state plan coordinate system,
then 89.34 will means 89.34 US-foot easting or northing from
that state plan zone's center reference point.
If your data is in ESRI's format,
you can't directly use other company's GIS product
because of formate incompatible.
This will economically benefit ESRI.
Step 2.
here is some geojson file sample
https://transparentgov.net/data/sample/geojson/dir.php
Step 3.
USGS publish current month earth quake in geojson format, how are you going to look at it?
copy this usgs earth quake geojson file path
https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_month.geojson
select any layer is fine, does not matter which layer,
but looking for blue box, all these model can load geojson file on map.
If your geojson file is remotely a URL link path, select model "url"
otherwise, your geojson file is physically on your hard drive, select model "upload",
https://transparentgov.net/json2tree/esri/server/folder.html?org=https%3A%2F%2Fpublic.gis.lacounty.gov%2Fpublic%2Frest%2Fservices&url=https%3A%2F%2Fpublic.gis.lacounty.gov%2Fpublic%2Frest%2Fservices&arcgis_online_token=&timeout=9000&select_folder=18&select_layer=18&select_folder_text=Political_Boundaries+%3Csup%3EMapServer%3C%2Fsup%3E&select_layer_text=18+%26%23x21E2%3B+County+Boundaries+%3Csup%3EFeature+Layer%3Csub%3E+esriGeometryPolygon%3C%2Fsub%3E%3C%2Fsup%3E
past geojson url here, click start button
Done.
https://transparentgov.net/json2tree/gateway/feature-geojson/url.html?_center_lat=3.885899739560747&_center_long=-154.45866197152353&_center_zoom=2&panto=0&url=https%3A%2F%2Fearthquake.usgs.gov%2Fearthquakes%2Ffeed%2Fv1.0%2Fsummary%2Fall_month.geojson
Step 4.
google map
https://transparentgov.net/json2tree/gateway/google-geojson/url.html?center_lat=61.96886349881883¢er_long=-150.83575949683674¢er_zoom=8&panto=0&url=+++++++++++https%3A%2F%2Fearthquake.usgs.gov%2Fearthquakes%2Ffeed%2Fv1.0%2Fsummary%2Fall_month.geojson
Step 5.