Friends used telegram so I had the app installed. It was easier to store documents in telegram than in one drive or proton drive, so telegram became my go too. Obviously not the best setup, but it worked and was easy. I’ll try out Signal and Matrix, but continence is a big factor in my choice.
If I want to share something with a friend, I can invite them to note chats or bulk forward files. Messages are separate, I can forward individual message rather than all messages. It’s more continent than notes apps I’ve tried.