A little usb module with 300m range is far from enough, as far as i wont get up my sit and going to run away with my lora node to test gateway code.
Again, while FTDI-based USB solutions have issues, range is not one of them. That was entirely due to the other poster’s install location.
So i dont look for full time grade gateway, but device which can easely be put on my backpack, with my laptop and when i have time, i can code. (lunch break at work for exemple).
Another option to consider would be leaving the gateway in a good location, and accessing it remotely. Even if I’m in the same room as one of my development gateways, I generally only connect to it with a serial cable when I’m working on basic OS setup or the scripts that enable remote access, otherwise I use the remote access to do work on the gateway. I’ll do trivial edits on the gateway, for more complex ones I edit it elsewhere and transfer it over. And while one can cross compile for the more capable compute platforms (pi, orangepi, etc) it doesn’t take that long to build on the device.
One of the other things about leaving a gateway in a given location is you can leave the nodes it interacts with in fixed locations, too. Some of my test nodes sit on their own remotely accessible pi supervisors - the pi has a copy of openocd and can reflash the node via a connection of chosen GPIOs to the node’s SWD pins, and the pi collects the node’s serial debug log, which I can either watch live or search back through. I usually have a node and SWD adapter with me, but often it’s faster to deploy to several in fixed installations and record how they interact with the network, plus then I don’t end up buried in cables.
But if you really want something portable, a concentrator board and a raspberry pi (or better yet something like an OrangePi model with eMMc) can be put in a small box. I’d avoid the pi zero as its interfaces are just too limited, in theory the gateway only needs SPI but if you wanted something like a GPS you could find yourself without a console serial port or needing to add a hub. And if you wanted to actually be a useful gateway you probably want wired Ethernet (or LTE) rather than wifi.