NG95 height - EPSG:5774

WKT

VERTCS["NG95_height", 
	VDATUM["Nivellement_General_du_Luxembourg"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["NG95_height", 
	VDATUM["Nivellement_General_du_Luxembourg"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "5774"]]

Data from @esri/proj-codes

{
  "wkid": 5774,
  "latestWkid": 5774,
  "macro": "PE_VCS_NG_L",
  "name": "NG95_height",
  "wkt": "VERTCS[\"NG95_height\",VDATUM[\"Nivellement_General_du_Luxembourg\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"NG95_height\",VDATUM[\"Nivellement_General_du_Luxembourg\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"5774\"]]",
  "description": "NG95 height",
  "authority": "EPSG",
  "version": "6.7(9.3.0.0)",
  "deprecated": "no",
  "areaname": "Luxembourg",
  "extent": {
    "slat": 49.44,
    "nlat": 50.19,
    "llon": 5.73,
    "rlon": 6.53
  }
}