Following up on this question, I am using an RN2903 module with a U.FL connector (with an additional option for a through-hole wire antenna). My PCB looks like this:
I used this coplanar waveguide calculator to set the impedance to 50 ohms, using a 30 mil trace width and 6 mil trace gap (with Er=4.8). I have done some preliminary signal strength tests, and for LoRa 900 MHz, it seems my own PCB is about 2 units lower in SNR than the Microchip RN2903 Pictail (which as the same track characteristics, but has a longer, curved trace as shown in my previous question).
My main concern is that my trace design is hindering the performance of the LoRa module. I have already attempted filling the wire antenna hole with solder, thinking this might improve performance, but improvements were only very slight. Additionally, I have seen these types of designs, such as this Adafruit module that has space for both an SMA connector and a through-hole wire antenna.
Do you see any definite NO-NOs in my design?
EDIT: Here is a picture of the PCB with the wire antenna hole filled with solder.