Here’s what I did to get this working.
add_action("rest_api_init", function () {
register_rest_route("options", "/all", [
"methods" => "GET",
"callback" => "acf_options_route",
]);
}
function acf_options_route() {
return get_fields('options');
}
Now the custom endpoint {{site}}/wp-json/options/all
will return all the site options.