I was interested in philosophy for quite a while because i) I thought utilitarianism was interesting but also ii) I wanted to see what other schools of thought were out there. For a while I was kind of confused since the other schools I heard about at first (e.g. Kantianism and virtue ethics) seemed to be really vague and I wasn't sure I saw anyone who actually believed them. [I still think that's largely true.]
But over time, I've read some things that I felt helped me understand various nonutilitarian perspectives more and generally enriched my understanding of philosophy. Here are a few I liked (organized a bit by theme). I don't claim to be super well-read; these are just some I learned from. A bunch are encyclopedia articles, some papers, some books.
It would be cool if others could share non-utilitarian writings they like!
Substantive Ethics
Methodology of Ethics
Have you read Meditations, by Marcus Aurelius? I highly recommend that book for you judging by the books you shared here.