Selfhosted

regarding the pricy enclosures, there are vastly cheaper eGPU solutions especially if you're able to utilise the on-board M.2 or mini-PCI slot. if you don't move the laptop around, it's a viable option. this would be an example - not an endorsment. you'd need a $15 PSU to power the graphics and it works well in linux, with the hotpluggability being the primary issue; if you're willing to shutdown before attaching the eGPU, close to no issues.

you can run it as graphics card (i.e. utilize its display outputs) or just use the laptop's display with optionally switching between the onboard and discrete graphics.

By the time you buy the enclosure you can get another old computer. Pickup a old workstation and put the GPU in it. Be mindful of power requirements

If you've got a thunderbolt port on your laptop and a thunderbolt dock on your laptop then there's no reason why it shouldn't work.

I'm not familiar with thunderbolt on linux, but on windows you plug it in and it just works™️ and shows up as if it was inside your machine. Your DE on linux might automatically do it, but if you're command line only you'll probably have to run a command first.

There are external GPU cases that might work with your laptop, but at least on older models these were relatively bandwidth limited which doesn't matter that much for gaming, but I guess it might cause more problems with AI workloads? On the other hand, maybe not if the model fits completely into the vRAM of the m40?