Thats it!!!
Thanks a lot for your great support.

Launching application is the last message in my log, there is no Create new xxx fetcher message at all.

just a test with config.js.sample:

> magicmirror@2.13.0 start /home/pi/MagicMirror
> DISPLAY="${DISPLAY:=:0}" ./node_modules/.bin/electron js/electron.js

[2020-11-16 20:21:35.961] [LOG]    Starting MagicMirror: v2.13.0
[2020-11-16 20:21:35.973] [LOG]    Loading config ...
[2020-11-16 20:21:35.982] [LOG]    Loading module helpers ...
[2020-11-16 20:21:35.985] [LOG]    No helper found for module: alert.
[2020-11-16 20:21:36.071] [LOG]    Initializing new module helper ...
[2020-11-16 20:21:36.072] [LOG]    Module helper loaded: updatenotification
[2020-11-16 20:21:36.073] [LOG]    No helper found for module: clock.
[2020-11-16 20:21:36.758] [LOG]    Initializing new module helper ...
[2020-11-16 20:21:36.759] [LOG]    Module helper loaded: calendar
[2020-11-16 20:21:36.761] [LOG]    No helper found for module: compliments.
[2020-11-16 20:21:36.763] [LOG]    No helper found for module: currentweather.
[2020-11-16 20:21:36.764] [LOG]    No helper found for module: weatherforecast.
[2020-11-16 20:21:36.831] [LOG]    Initializing new module helper ...
[2020-11-16 20:21:36.831] [LOG]    Module helper loaded: newsfeed
[2020-11-16 20:21:36.832] [LOG]    All module helpers loaded.
[2020-11-16 20:21:37.020] [LOG]    Starting server on port 8080 ... 
[2020-11-16 20:21:37.046] [LOG]    Server started ...
[2020-11-16 20:21:37.048] [LOG]    Connecting socket for: updatenotification
[2020-11-16 20:21:37.050] [LOG]    Connecting socket for: calendar
[2020-11-16 20:21:37.052] [LOG]    Starting node helper for: calendar
[2020-11-16 20:21:37.054] [LOG]    Connecting socket for: newsfeed
[2020-11-16 20:21:37.057] [LOG]    Starting node helper for: newsfeed
[2020-11-16 20:21:37.058] [LOG]    Sockets connected & modules started ...
[2020-11-16 20:21:37.193] [LOG]    Launching application.

All calendars that I have tested show “loading”, but no calendar entry is shown.

my config.js

/* Magic Mirror Config Sample
 *
 * By Michael Teeuw https://michaelteeuw.nl
 * MIT Licensed.
 *
 * For more information on how you can configure this file
 * See https://github.com/MichMich/MagicMirror#configuration
 *
 */

var config = {
	address: "localhost", 	// Address to listen on, can be:
							// - "localhost", "127.0.0.1", "::1" to listen on loopback interface
							// - another specific IPv4/6 to listen on a specific interface
							// - "0.0.0.0", "::" to listen on any interface
							// Default, when address config is left out or empty, is "localhost"
	port: 8080,
	basePath: "/home/pi/MagicMirror/", 	// The URL path where MagicMirror is hosted. If you are using a Reverse proxy
					// you must set the sub path here. basePath must end with a /
/*	ipWhitelist: ["192.168.1.5", "::ffff:192.168.1.5", "::1"], 	// Set [] to allow all IP addresses */
	ipWhitelist: [],
															// or add a specific IPv4 of 192.168.1.5 :
															// ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.1.5"],
															// or IPv4 range of 192.168.3.0 --> 192.168.3.15 use CIDR format :
															// ["127.0.0.1", "::ffff:127.0.0.1", "::1", "::ffff:192.168.3.0/28"],

	useHttps: false, 		// Support HTTPS or not, default "false" will use HTTP
	httpsPrivateKey: "", 	// HTTPS private key path, only require when useHttps is true
	httpsCertificate: "", 	// HTTPS Certificate path, only require when useHttps is true

	language: "de",
	logLevel: ["INFO", "LOG", "WARN", "ERROR"],
	timeFormat: 24,
	units: "metric",
	// serverOnly:  true/false/"local" ,
	// local for armv6l processors, default
	//   starts serveronly and then starts chrome browser
	// false, default for all NON-armv6l devices
	// true, force serveronly mode, because you want to.. no UI on this device

	modules: [
		{
			module: "alert",
		},
		{
			module: "updatenotification",
			position: "top_bar"
		},
		{
			module: "clock",
			position: "top_left",
            config: {
                // See 'Configuration options' for more information.
            }
		},
        {
            module: "calendar",
            position: "top_left",   // This can be any of the regions. Best results in left or right regions.
            config: {
                maximumNumberOfDays: 28,
                maximumEntries: 10,
                calendars: [
                    {
						symbol: "calendar-check",
						url: "http://www.calendarlabs.com/ical-calendar/ics/76/US_Holidays.ics"
                    }
                ]
            }
        },
	]
};

/*************** DO NOT EDIT THE LINE BELOW ***************/
if (typeof module !== "undefined") {module.exports = config;}

.pm2 log:

> magicmirror@2.13.0 start /home/pi/MagicMirror
> DISPLAY="${DISPLAY:=:0}" ./node_modules/.bin/electron js/electron.js

[2020-11-16 16:48:10.759] [LOG]    Starting MagicMirror: v2.13.0
[2020-11-16 16:48:10.807] [LOG]    Loading config ...
[2020-11-16 16:48:10.819] [LOG]    Loading module helpers ...
[2020-11-16 16:48:10.824] [LOG]    No helper found for module: alert.
[2020-11-16 16:48:10.951] [LOG]    Initializing new module helper ...
[2020-11-16 16:48:10.952] [LOG]    Module helper loaded: updatenotification
[2020-11-16 16:48:10.955] [LOG]    No helper found for module: clock.
[2020-11-16 16:48:12.121] [LOG]    Initializing new module helper ...
[2020-11-16 16:48:12.122] [LOG]    Module helper loaded: calendar
[2020-11-16 16:48:12.123] [LOG]    All module helpers loaded.
[2020-11-16 16:48:12.445] [LOG]    Starting server on port 8080 ... 
[2020-11-16 16:48:12.481] [INFO]   You're using a full whitelist configuration to allow for all IPs
[2020-11-16 16:48:12.496] [LOG]    Server started ...
[2020-11-16 16:48:12.497] [LOG]    Connecting socket for: updatenotification
[2020-11-16 16:48:12.498] [LOG]    Connecting socket for: calendar
[2020-11-16 16:48:12.499] [LOG]    Starting node helper for: calendar
[2020-11-16 16:48:12.500] [LOG]    Sockets connected & modules started ...
[2020-11-16 16:48:13.056] [LOG]    Launching application.

I can’t see any create fetcher message at all.
Thanks a lot for any support.