“The Circle” by Dave Eggers https://en.wikipedia.org/wiki/The_Circle_(Eggers_novel)

I wrote a blog article about creating a second brain some time ago. It’s meant mostly for programmers, but the concepts hold true for other people as well :) https://blog.sewera.dev/second-brain

You can also try VSCodium with Foam, I think both are FOSS. You can read a bit about this setup on my blog: https://blog.sewera.dev/second-brain