https://config.qmk.fm

Install qmk cli and clone repo into this dir
cp swatson-keymap.c qmk_firmware/keyboards/sentraq/s60_x/keymaps/swatson-keymap/keymap.c && qmk compile -kb sentraq/s60_x/rgb -km swatson-keymap

then use dfu-programmer to flash directly

use dfu-programmer:
sudo dfu-programmer atmega32u4 erase
sudo dfu-programmer atmega32u4 flash $path_to_hex
sudo dfu-programmer reset