In itself, it works without a graphics card, but then you can only use the USB & RJ45 ports (which of course makes absolutely no sense for this price). If you want to use it as an eGPU, you have to install an additional graphics card (which is not included and has to be ordered separately). The latest graphics card models should all work, but older ones might have problems. So far I have tried the eGPU with the following graphics cards and all have worked without problems: GTX 1650 TI, RTX 2070S, RTX 2080S.
Although this is not part of the question I would like to add that you need a Thunderbolt 3 port on the notebook, a pure USB-C port is NOT sufficient. (I have already seen several times that several users have not taken this into account).