Thanks for all the answers. Is there any possible (other) way except using an USB extension cable to a wireless operation of my RPI 4 at a 6 feet distance?
Not unless you want to replace your keyboard. The extension cable is the cheapest way for a quick fix. My problem was with an Intel NUC. Before installing the USB extension cable, my max distance was only a few feet. It was probably due to interference between the NUC and the USB Dongle.