The instructions to put the Arduino into DFU say I should shortcut briefly the 2 leftmost ICSP headers next to the USB port. But my board does not have them. Does anybody know what are the right headers or if it is at all possible to set my board into DFU mode?
It has a CH340G usb serial adapter, which cannot be reprogrammed and has no DFU mode.
If you are looking for DFU mode because it's not detecting correctly and you think it's because the 16u2 isn't programmed correctly, the problem is probably that you need to install the CH340G drivers, not the normal Arduino drivers.
If you are looking for DFU mode for some project that requires custom firmware on the CH340G, that board is not usable for that project, you will need to get a faithful clone of the Uno, which has the 16u2, not the CH340G based ones
If you want to use your Arduino as a HID device you need the DFU mode
If you use this library which supports UNO/MEGA/Leonardo/(Pro)Micro/ any 8u2/16u2/at90usb8/162/32u2/32u4 compatible board and some more BUT you need an 16u2 chip