When on the road I have found that duct-taping the Z3C to a window often makes the difference between a workable connection and no connection. Unfortunately, rolls of duct tape take up a lot of space in a computer bag.
Warning - many of those lovely double/triple glazed glass buildings have metallic coatings on one of the glass layers, this can block signals completely.
I notice that the MG range is described as having a CAT6 cellular modem - up to 300Mbps. So not 5G.
When I go up to London, despite the UK rarely being an early adopter in these matters, I have 4 live 5G networks to choose from. It would have been nice to think that the MG had been developed with 5G in mind.
I have checked the size and weight of the MG 21 (160.45 x 160.45 x 34.45mm and 497g). This set me thinking.
I think that I can stick a Velcro patch on the glass of a window and also on the back of the MG, to hold the MG firmly in place (worst case, Superglue the Velcro to the window, using Acetone as a solvent to remove it).
If I'm using a Z3C, it has an 802.3af 15.5W PoE port, and the MG21 draws 10 Watt Maximum also PoE 802.3af, whilst being a similar weight. So I could velcro the MG21 to the window and keep the Z3C on my desk. If only they would allow the Z3C or MG21 to access a WiFi network . . .
It would probably be easier to fit the MG21 into the computer bag than a roll of duct tape.
Now, all I need to do is get hold of a MG21 for testing and proof of concept.