Logseq is a privacy-first tool for thought.

Similar to Roam's technique of letting the notes flow with links to each other.

Every topic is its own flat file. Nothing is better than keeping your data in the file system with an option of git source control or online backup.
https://www.inkandswitch.com/local-first/

The daily journal feature allows you to quickly capture disparate topics under today's date and by way of tags make things organized and findable from any topic page.

Logseq is opensource.

Lots of apps are too graphically flexible in how they allow content to be entered, placed, and formatted. They act like Word when what you want when authoring content is Markdown. Content and semantic structure, not graphical frills.

Logseq support Emacs Org syntax out of the box.