>> There's a lot of technical debt that needs to be paid, but it's getting better.

You should just leave these sort of statements out of your introduction. It's generally assumed all projects have some degree of technical debt, and you'll lose more users (i.e. most) than you'd gain (i.e. 0) by trying to treat the subject with candor.

In other words, don't sell yourself short. Speak directly to why someone would want Sortix right away. In your intro, speak as if Sortix exists, fully formed, and complete. Let people come to their own conclusions about the quality.

For example, I'd rewrite the opening sentence from

    Sortix is a small self-hosting Unix-like operating system developed since 2011 aiming 
    to be a clean and modern POSIX implementation.

To

    Sortix is a clean and modern POSIX implementation.

Believe me, I've never released a project that I thought was complete. That's not because I've never released a project, it's because I'll probably never consider any of my projects "complete". There will always be more to add, more to take away, more to do. It adds nothing to my description to call my projects incomplete. The game is thus figuring out when to cut my engineering-self off and engage my sales-self.