I think I have solved the problem, now able to force RUT240 to use 3G (Telenor SIM).
I had to configure the Network Code to 24024 manually, see picture. It doesn't even show up as possible, but it is the network code of the 3G network built by Tele2 and Telenor together.
Teltonika should revise the code, taking into account that the Network Code may be different from 2G to 3G to 4G.