I’ve only had a brief look and test so far, but I’ll be testing this out a lot more. Obsidian is free to use but not open source software, Capacities is the same with a generous free option and is not open source software either.
Something quite different, but useful, is that Capacities is cloud synced first, so the various clients all sync via the cloud for free (unlike Obsidian which can be a bit clunky via Syncthing or similar sync software).
Obsidian is more offline first in Markdown format for full portability between other note apps. Capacities however does export (and backup) to various formats including PDF, Markdown, MS Word, and Latex. I’m just not seeing a bulk export yet of selected notes (called pages in Capacities) to these various formats. I’m testing this a bit more still.
Getting some notes from Obsidian into Capacities so far was just a matter of copy and pasting. I just had to copy and paste any images separately into the note. Tables, code snippets, headings, etc all came across perfectly.
Speaking of code snippets, I do really like that you can tag each one as a bash script, Python code, Lua code, etc, and it does a great job of syntax highlighting (something I was not seeing in Obsidian).
Capacities does not yet have all the plugins that Obsidian has, but for many who were thinking of starting to use Obsidian, Capacities may be a good option to consider.
I’ll also be interested to see what the Linux app (in development) stores locally and how well it works offline. There are already desktop apps for macOS and Windows (and mobile apps for Android and iOS).