Do you like hiking, but wish it was harder? Do you want everyone on the trail to know you are better than them? Then you should try trail running!
Trail running is just running whenever you're around people, and hiking when you're not.
If you're travelling in Norway, there's great official trail resources like Kartverket, UT.no, and The Norwegian Trekking Association (DNT). Kartverket even offers free maps. UT provides free GPX files.
Official maps and OpenStreetMap have better coverage than any commercial trail or hiking platform, and they're free. Support them.
Remember to read the mountain code if you haven't yet. Also don't forget sunscreen.
Trail running has a very low barrier-of-entry. All you really need is a trail, but it's a good idea to get some decent shoes. Look for trail running shoes that fit you well. If you're running on muddy or wet trails, get shoes that dry quickly.