I can't get pressure to work properly in inkscape for linux. It works fine with gimp, when I set it up with input devices. However it doesn't work when I do exactly the same for inkscape. I've also pressed/activated the pressure sensitivity button in the calligraphy tool.

Welcome to InkscapeForum!

I don't use a tablet, so can't offer any advice. But questions about pressure sensitivity have been addressed many times in this forum, over the last several years. Until someone who knows the answer comes along, you may well find the solution by searching the forum

Which linux?

(If Ubuntu, see this report)

It perhaps worth checking if it's never working or if it works for a while when you change the settings, but never restores the settings (no settings at all).

It's important to note that (to me at least) despite of the settings panel saying that sensitivity requires restart, it really doesn't. And (again, with me at least) it will actually do the opposite, make it not work as I restart, because it will work fine but it only lasts until I close inkscape.

I'm using debian testing, it happens with the stable, testing, unstable and experimental inkscape versions (all tested on debian testing), and it also happens with an ubuntu version (also tried on debian).