Even a basic custom field formatter like below, makes the Edit in Gridview search render and empty listbox. I've tried @currentField.lookupValue in place of the [FieldName].lookupValue with the same result.
formatter:
{
"$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
"elmType": "div",
"txtContent": "[$HG_x0020_Test.lookupValue]",
"debugMode": true
}