I’ve been a heavy user of Zim for as long as I can remember, before then, plain text notes with more command line fun using Joe, Vi, Emacs or more recently Vim. The aim has been to keep content as future-proof as possible. In the end, I decided to just shift everything to markdown. As a language it’s eminently readable across multiple platforms.
I took a look at Obsidian (for the second time) this year, and decided to do a full export. (Zim has the option to just export your entire notebook - or a page if you just want a singular item). Copying the export to the Obsidian folder was all I had to do, and the structure was maintained and ready to go.
I’m a little amazed at how good Obsidian is, - particularly with the functionality around plugins and css snippets. It’s markedly more customisable than Zim, - and easier to get to those changes. If you’re looking for a decent note-taking app, I think it’s worth a look. I’ve run through the full circle, Zim, Joplin, Cherrytree, Org Mode, Vim (text), and Obsidian, while not completely open source, ticks enough boxes that for me, it’s worth holding on to for local notes.