QLandkarte makes use of the device plugins developed for the original QLandkarte project. One way to connect your Garmin is to install the plugins from the old project.

A much better way is to support the new Garmin Device Driver project. It is a standalone project decoupling the plugin development from QLandkarte. If you see that your device is not supported on the OS you prefer, take the time to port the existing code from original QLandkarte or add your device as new one. This is crucial as I will only support the GPSMap60SCx driver on Linux. I have no chance to test anything else. Thus I need your help.

To make a plugin is easy. Plugins are no real drivers. They are just converting data into a bytestream on the USB or serial interface and vice versa. If you have a look at the code you will see that it is mostly copy-n-paste and some bashing around with CMake.

There is a difference between QLandkarte GT and original QLandkarte when uploading maps. The old version kept the complete map image in memory. That was bad for small PCs. QLandkarte GT will make a temporary file and pass the file name to the driver. However that needs a new API call. Thus if you like to upload maps to any other device than those based on the GPSMap60SCx driver you have to get involved.

[1] not tested.