For short form note taking, WhatsApp is actually the best option I've found. It's fast, secure, available on all my devices, synchronised, searchable and free.
I tend to write two kinds of note: long and short. Long notes I store in Notion - and they are essentially personal documentation. I'm talking recipes, packing lists, code snippets or movie recommendations - things that need to be stored in different formats, with rich text, images, and more.
But the vast majority of notes are short - and for these, Notion is too slow. The best app I've found for short notes is WhatsApp.
To use WhatsApp for note taking, you need to be able to send yourself messages, which is a weirdly un-straightforward process.
You have two options, either send yourself a direct message, or create a group. I prefer the group option, but I'll show you both.
This will prompt you to open a chat with yourself - why you can't select your own contact from the UI, I have no idea. ¯\_(ツ)_/¯