I’d look on strava for clubs, look at who has KOMs as they’ll know the routes and where to go; do a bit of Strava stalking and you’ll find tons of info. Crush it dude
Welcome to Germany and thanks for your service!
I was living in Cologne pre consumer gps devices therefor I don’t have any routes at hand but for pikepacking I wouldn’t go east from Geilenkirchen. I would ride into the direction of Eifel (south) or the Ardennes (Southwest) or to the west, in the direction of North Sea.
I second Komoot. It’s actually a German company. It’s quite popular and there are a lot of ratings for the different streets. This gives you a good idea about popular routes.
An other advise: In Germany it’s super easy to take your bike on trains. Some even have dedicated bike-cars. You might have to buy a ticket for a couple of EUR. So a weekend in the Alps is just a few hours away for you.
Regarding bikepacking. One of the most famous routes is riding along the Rhine (flat and a lot of dedicated cycling paths). Probably it’s also popular because it’s populated with vinyards. Head over to Cologne, ride down south via Bonn, Koblenz (and get a new Canyon or just visit their store, it’s quite nice) and continue to Mainz! Good times!
I would echo komoot and also suggest strava heat maps. I would subscribe for these two for a year until you make regular routes for yourself and learning the environment.
Another point is having a proper head unit to get car like navigation.
These things really payback if your time is limited and trying to maximize the fun outside.