Been awhile since I saw a thread like this and they’re always good for at least one or two things I’ve never heard of before. Bonus points if the software is open source and cross platform. Extra bonus points if you link to where we can see it/get it.

My contribution: Destiny which is an anonymous, P2P, E2EE file sharing app - its basically a GUI for a Magic Wormhole implementation. Works on Linux (tarball or appimage), Win, Mac, Android (inc f-droid) and iOS. Only downside is it’s not been updated for 2 years.