In general, you can not update even the dedicated GPU, which is probably referred to when you use the expression "external graphics card", since it is almost always soldered to the main board. The only difference between integrated and dedicated GPUs is that the integrated GPU is usually part of the CPU chip and is much less powerful than the separate dedicated GPU chip, which usually also has its own memory. However, some modern laptops are compatible with Thunderbolt and you can use them to connect a real external desktop GPU in a cabinet using usually a USB type C cable. So, it is basically a box that you can connect to your laptop that requires your own power supply and that, in general, is the only reasonable way to update graphics on laptops.
There are also springs for certain laptops that may contain a GPU.