By the way, I received another tip from elsewhere to apply some elastic caulk in the joint to prevent cracking. Could it work? Isn't there a risk that the painted surface might still crack even if the joint itself is elastic?
Check out, for example, gyproc's website, where there are excellent instructions on what to do and not do. For instance, elastic sealant is not recommended, which makes sense. The movements in the elastic joint will, as you suspected, cause the paint or wallpaper to crack instead. Paper tape and filler make the surface appear as a single large plasterboard without seams, while elastic sealant or fiberglass tape creates a joint that moves more easily than the rest of the surface, which in turn can lead to cracking if the framework moves.
Check with norgips.sverige@norgips.com where they have retailers.