Go to this page if you are interested in building a Zettelkasten. Although it is not my aim to take notes and develop ideas in exactly the way the German sociologist Niklas Luhmann did, in the posts on that page, I lay out how to build a Zettelkasten in a way that I believe is a bit more in keeping with how Luhmann did things than is "the Zettelkasten method" that many videos and blog posts claim to explain. (I should add, though, that my aim is not to do exactly as Luhmann did when it comes to taking notes and developing ideas.)
To learn why there is no such thing as "the Zettelkasten method," check out this piece by Chris Aldrich (October 2022). See also Scott Scheper's Antinet Zettelkasten (December 2022), pp. xvii–xviii and Chapter Three, "The Current Zettelkasten Landscape."
Obsidian is currently my note-making app of choice. I still use plenty of other apps to supplement the work I do in Obsidian, but Obsidian's the main one for me. For my posts on Obsidian, click here.