+1 for Joplin. You can self-host it. If you do, you can share notes between the users of the server. I wrote a tutorial on how to install it with docker. Should you need it, pm me.

Dick Dastardly

Straighten it, drill a small hole perpendicular to the hinge of one of your doors, put it inside and cover the hole up. If there’s enough time, add some paint to it, otherwise just use the sawdust mixed with some glue. The hole is certainly tiny enough to get unnoticed and any metal detector would hopefully pick up the larger metal hinge instead of the paperclip. Finally, if you also paint it up, it would practically be invisible. Just make sure you use a paint that doesn’t smell too strongly.