Do you want to use an old laptop as DEX station for your Samsung galaxy S8 / S9 / S8+ / S9+? An xda developer user was able to get that done. He used his 17.3” Acer laptop for it. Here is what he did – he removed the motherboard and rest of the electronics from it.
He then removed the HD+ panel and replaced it with a full HD panel. You can skip this part as HD+ / HD would work just fine with the Galaxy phone. However, full HD is recommended for crisp text and pictures.
Anyway, irrespective of the display you use, just use an HDMI to EDP converter board with the phone.
Then, install some voltage transformers, a 2×3 Watt audio amplifier for the laptop speakers, a charging board, a 5v fan and an USB Hub. Connect the phone with the USB C MHL cable and if you want to use speakers, use an audio cable.
For some reason, the built in laptop keyboard did not work and he had to use a Bluetooth keyboard with built in touchpad instead.
Battery of laptop is not working but you can connect a power bank for that instead to keep your phone charged.
Here is a video of it.