Ctrl + shift + alt + win + any letter opens office apps
W - Word
P - PowerPoint
T - teams
N - OneNote
...etc
LinkedIn just happens to be L. If there isn't an app installed (or available) it'll just open in your browser.
I actually found these a few years ago when I decided to press every modifier letter combination. Back then it wasn't documented anywhere but I've seen it pop up a few times in the last month so somebody must've found and shared it recently