The short answer is yes you can. There's a slightly longer answer to follow...
Using an IR filter is very much like using any other filter with the exception that unless the camera (any camera) is specifically converted to capture IR then you'll be faced with slower/longer shutter speeds which mean that you'll be forced to shoot on a tripod. The longer shutter speeds will also mean a blur in the clouds and anything else that might have some movement.
A converted camera can be used handheld much the same as it was prior to the conversion. The non converted camera will offer near same results but will take much longer shutter speeds.
You'll also need to be aware that some lenses create what is called a "hot-spot" or bloom of light in the center and can be found on both converted and non-converted cameras.
The non-converted camera will also need to be focused manually without the IR filter attached then switched to manual to keep the focus point. Just focus, install the filter and using a remote shutter snap the image.
I've shot non-converted IR images using mirrorless as well as medium format systems with great results. I've also converted mirror and mirrorless cameras using various IR with even better results. The best platform to us in IR is a mirrorless camera as you see what the sensor sees as you are composing the frame.
So the longer answer is yes, you can use a 830nm or any IR filter on a GFX. I know because I've done it.
Best of luck and welcome to the IR world!
Don