I managed to solder the resistor into Arduino's Atmega8u2. The I reset atmega8u2 and by wiring the pins mentioned in: https://www.arduino.cc/en/Hacking/DFUProgramming8U2

I can confirm it via this message over my GNU/Linux machine by running dmesg:

[ 1544.679504] usb 1-6: new full-speed USB device number 42 using xhci_hcd
[ 1544.808341] usb 1-6: New USB device found, idVendor=03eb, idProduct=2ff7
[ 1544.808350] usb 1-6: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[ 1544.808356] usb 1-6: Product: Arduino Uno DFU
[ 1544.894365] [UFW BLOCK] IN=enp3s0 OUT= MAC= SRC=fe80:0000:0000:0000:5446:7c23:5247:7096 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=924209 PROTO=UDP SPT=8612 DPT=8612 LEN=24 
[ 1544.894381] [UFW BLOCK] IN=enp3s0 OUT= MAC= SRC=fe80:0000:0000:0000:5446:7c23:5247:7096 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=486391 PROTO=UDP SPT=8612 DPT=8610 LEN=24 
[ 1544.904703] [UFW BLOCK] IN=enp3s0 OUT= MAC= SRC=fe80:0000:0000:0000:5446:7c23:5247:7096 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=924209 PROTO=UDP SPT=8612 DPT=8612 LEN=24 
[ 1544.904714] [UFW BLOCK] IN=enp3s0 OUT= MAC= SRC=fe80:0000:0000:0000:5446:7c23:5247:7096 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=64 TC=0 HOPLIMIT=1 FLOWLBL=486391 PROTO=UDP SPT=8612 DPT=8610 LEN=24 

The I try to run:

sudo dfu-programmer atmega8u2 erase

But for some reason I get the following error: dfu-programmer: no device present.

Do you know why I get this error and how I can fix it?

#Edit 1 I installed the latest version of dfu-programmer and compiled from source via https://sourceforge.net/projects/dfu-programmer/files/dfu-programmer/0.7.2/ but still I get the error.