RGM04 (lon-lat) - EPSG:7039

WKT

GEOGCS["RGM04_(lon-lat)", 
	DATUM["D_Reseau_Geodesique_de_Mayotte_2004", 
		SPHEROID["GRS_1980", 6378137.0, 298.257222101]], 
	PRIMEM["Greenwich", 0.0], 
	UNIT["Degree", 0.0174532925199433]]

WKT2

GEOGCRS["RGM04_(lon-lat)", 
	DATUM["D_Reseau_Geodesique_de_Mayotte_2004", 
		ELLIPSOID["GRS_1980", 6378137.0, 298.257222101]], 
	PRIMEM["Greenwich", 0.0], 
	CS[ellipsoidal, 2], 
	AXIS["Longitude (lon)", east, 
		ORDER[1]], 
	AXIS["Latitude (lat)", north, 
		ORDER[2]], 
	ANGLEUNIT["Degree", 0.0174532925199433], 
	ID["EPSG", "7039"]]

Data from @esri/proj-codes

{
  "wkid": 7039,
  "latestWkid": 7039,
  "macro": "PE_GCS_RGM04_LON_LAT",
  "name": "RGM04_(lon-lat)",
  "wkt": "GEOGCS[\"RGM04_(lon-lat)\",DATUM[\"D_Reseau_Geodesique_de_Mayotte_2004\",SPHEROID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]",
  "wkt2": "GEOGCRS[\"RGM04_(lon-lat)\",DATUM[\"D_Reseau_Geodesique_de_Mayotte_2004\",ELLIPSOID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],CS[ellipsoidal,2],AXIS[\"Longitude (lon)\",east,ORDER[1]],AXIS[\"Latitude (lat)\",north,ORDER[2]],ANGLEUNIT[\"Degree\",0.0174532925199433],ID[\"EPSG\",\"7039\"]]",
  "description": "RGM04 (lon-lat)",
  "authority": "EPSG",
  "version": "8.7.1(10.5.0)",
  "deprecated": "no",
  "areaname": "Mayotte",
  "extent": {
    "slat": -14.49,
    "nlat": -11.33,
    "llon": 43.68,
    "rlon": 46.7
  }
}