Halacha meter recommendations

I'm writing from a cell phone, and I made a few mistakes. I meant that I was interested in learning ‘meta halakhah’ (about the authority of the Shas, regulations, etc.). I'm interested in learning from the sources, not from summaries of contemporary authors. Can you recommend something?

I don't know, except for the Rambam, who is the one who carries the tools. There is also some in the booklet of the Sophists of R. Elchanan and Sarman.

I remember that the rabbi brings the sermons of Beit Yishai and also the roots in Rambam, right?

Beit Yishai doesn't really deal with this. But you can see it in the sermons section of 15.
There is no direct discussion in the roots. We had a discussion in this around the first two roots.