What is possible and what is practical are two entirely different things.
For example I have a 4070 laptop GPU. What if I want to send it to a repair shop to only upgrade that since I’m more than happy with every other component, especially with my 240hz screen.
By the time you tracked down the part, assuming not only compatibility with your motherboard but also that the shop could even do this job, you’d be better off simply selling the laptop you have and using those funds toward something with a better GPU.
You’re right—it might be easier to sell the laptop for an upgrade, but if the 240Hz screen and other specs are important to me, finding a replacement with similar features could be tricky.
The closest thing I’ve seen to this is someone building a gaming laptop from of desktop components; is this possible? Probably if you have the knowledge, but is it useful? Probably unlikely, and even if it was, it would be quite expensive, especially if you were just trying to upgrade a laptop GPU at that point, which makes little sense. You might as well buy a completely new laptop. Even with a BIOS update, you must consider that the CPU and motherboard are also outdated. There are many elements that need to be put in here, but at the end of the day, it’s just not worth it in my opinion.