I've used the same system for about 8 years. I have a folder of Markdown files labeled "diary"; in that folder are files named YYYY-MM-DD.md. I use these files as a daily scratchpad, recording what needs to be done, what I accomplished, and notes from meetings, conversations, etc.
I originally created this system when I was using vimwiki, but it is compatible with Obsidian's Daily Notes feature too (a big advantage to using A Folder of Markdown Files as a knowledge base). In fact, the two can share a diary without undue effort.
Obsidian does charge for sync, but you don't have to use their sync service. You can sync yourself using syncthing, dropbox, or whatever you like. I use git to sync, with the obsidian-git plugin[1].
I originally created this system when I was using vimwiki, but it is compatible with Obsidian's Daily Notes feature too (a big advantage to using A Folder of Markdown Files as a knowledge base). In fact, the two can share a diary without undue effort.
Obsidian does charge for sync, but you don't have to use their sync service. You can sync yourself using syncthing, dropbox, or whatever you like. I use git to sync, with the obsidian-git plugin[1].
[1] https://github.com/denolehov/obsidian-git