I found the following information on pages 69 and 70 of the operating instructions:
https://www.studerus.ch/de...
According to this information, it should be possible to select a specific carrier for the 5G band, as well as whether the router should automatically switch to a better signal or even LTE.

I bought the device myself and wanted to add it here with a screenshot, I am very satisfied with the band selection! https://i.imgur.com/3hnNJIb.pn...