Hi, my mistake was assuming that this antenna https://sixfab.com/product/lte-5g-sma-high-performance-blade-antenna/ could also work for GNSS. Even though it covers the GNSS spectrum, the specs are probably unsuited for GNSS reception.
Solution.: Get a different antenna.
It might be helpful to note that in the 5G dev kit documentation, with a suggestion for a GNSS antenna.