I used many different things over the years
Depending on the life expectancy of the note and its goal, it nowadays fall in one of 2 categories:
- a snippet I want to organize and be able to share later, something more long-lived: I love Dropbox paper (paper.dropbox.com) it made me move away from Keep and Evernote and things like that. Works well on mobile, awesome on desktop, fast, brilliant
- for anything which is work-in-progress, notes before to clean up and write a real doc, .... I use a 'notes' folder in which I write down markdowns, and open that 'project' in either Atom or VSCode. That 'notes' folder is inside Dropbox so that I can keep my notes on my laptop, desktop, phone... What I like with this approach is that you get the benefits of dropbox, and all the convenient features of your usual tools (key bindings you're familiar with, syntax highlighting, search, whatever
Oh, and pen and paper are still very useful and valuable ;-)