I have a T580 with nVidia graphics. Repairability is great. You can find a manual with step-by-step instructions for every part online.
But the thermals in that thing are awful. Especially on Linux and doubly so with the GPU. It has some stupid on-lap detection which heavily throttles the system to not burn the user. Up until a few years ago there wasn’t a driver for Linux so it always defaulted to on-lap-mode. But even worse, the GPU has some hardcoded 70° limit and it throttles down to the lowest clockrate when it reaches that. And it reaches that quickly because CPU and GPU share a heatpipe.
Nowadays I just run it on the integrated Intel graphics on Wayland and it’s great. But it would be cool if I could use the GPU that is at least theoretically able to run Doom 2016 at 30 fps. But practically it struggles with Quake 3.
It’s just a shame that you probably won’t know about these kinds of problems on a new laptop because people only notice them after a few months to years.