Hello @csluiter! Welcome.
It actually is included in the nRF5 SDK that Nordic includes. The instructions aren’t front and center in the post, but they can be found on the Github example page: https://github.com/memfault/interrupt/tree/master/example/firmware-shell#setup
$ cd nRF5_SDK_15.3.0_59ac345/
$ find . -name "sdk_common.h"
./components/libraries/util/sdk_common.h
p.s. I enjoyed reading your posts so much I bought the dev board you’re using to try out the examples. It’s been a steep learning curve so far, but it’s a good challenge!
That’s awesome to hear! The nRF52 board is great and easy to use. You won’t be disappointed.