Optiboot (an older version) is installed by default on the Arduino Uno and (as of 2018) official Arduino Nano boards. It can be installed on all older mega8, 168 or 328 based Arduinos. As of 2019, ...
tinygo flash -target=arduino -port=/dev/ttyUSB0 . If everything goes OK, some progress bars should pop up and the process should end with a thankful message: avrdude: verifying ... avrdude: 7036 bytes ...