My router is an apu2c4 which has no graphical hardware interface …
I remember in the beginning of it there were things like a serial terminal available
(a display with serial port and a keyboard) i guess this is hard to find…
How can i realize at least a display at the apu 2c4 ?
The system console on the APU system is on the serial port ( RS232, V.24, … ).
You access this console with a good old terminal ( VT100 or others ) or with an USB serial adapter and terminal software ( PuTTY for example ).
Configuration of IPFire is mainly done by the WebGUI or SSH.
The serial console is needed for installation or troubleshooting of systems with broken networking only.
you are at place of your IPFire. With a laptop with USB adapter and terminal emulator you can watch the output. Or you buy an used real terminal ( no idea how the prices are ).
you want to watch from your working place, not in the installation room. A little computer ( Raspi for example ) with serial connection and terminal software can transport the data via ethernet to your working place.