My recommendation would be to use Logseq.

It’s similar to Obsidian (“Second Brain”/ PKM), but with the journal function as backbone.

It relies heavily on crosslinking, is markdown-based, very efficient and a joy to use once you “got” it, and supports a hell lot of features, including TODO, plugins, and much more.

I use it for everything and pretty much never loved a piece of software this much!
It sounds like it is THE tool you’re searching for!