@SE-Fredd I want to say that I managed to solve my issue with using an external antenna with this router. A neighbour had a smaller TP-link 4G router (MR200 I think it was) on the shelf and I tried...

@Kevin_Z I also have the Archer MR600 4G router (in Sweden). It works OK with the included antennas, especially after finding the best spot in the house. But I cannot get it to work with an external...