The Thingy91 GPS system sensitivity is terrible. Getting the GPS to lock on takes forever, and many times doesn't lock on at all, and if it does lock loses the connection regularly. Sensitivity is 20 dB less than for a normal GPS receiver and is due to the RF front end using a cellular antenna instead of a normal circularly polarized antenna with zenith pattern. Luckily there is an external antenna port, I assume because Nordic engineers recognize the cell antenna solution is not going to work for most applications. How about recommending a specific external antenna you know works well and comes with the highly unusual SMF connector on your board?