Obsidian or Logseq.
I've used Logseq for my lab journal, thoughts, and whatsoever, and it works excellent for that.
- You can link different things/ dates with each entry
- Markdown
- Functions and querys
- Local
- Very flexible
- And you can find pretty much every thought you've ever had, nothing is lost.
It can be tricky tho if you want to collaborate, because the sync isn't perfect yet, but the devs are working really hard on it