The battery life is much worse than on Windows, can't deny that.
0: https://bauklimatik-dresden.de/privat/nicolai/index.html?htt...
One of the problems I've ran into is that my external 4k monitor (40") runs at 100% scaling and my laptop 4k monitor at 200%, which causes all sorts of rendering bugs. After some searching I found that this has nothing to do with the X1E or Ubuntu for that matter. It's a X11/Wayland issue that just isn't properly implemented yet.
Edit: it looks like this guide also instructs to switch to 'discrete graphics' in the BIOS. This is a hack and not what you want. This causes the nVidia graphics chip to be always on (instead of letting the OS choose). This causes terrible battery life. Don't do that.