From my perspective, this is *almost* perfect for the development category. You are developing an OS project and writing about the updates. That's exactly what Utopian is for. The only changes I would suggest are to start creating a branch for each weekly update, then submit a PR highlighting the changes you made (not strictly necessary to make a PR per the rules but would help the moderator). You might have to shift your writing a little more towards release vs journal which is something only you can decide if you want to do, would vary on who the mod was though.

Personally, I feel like the blog post category is more aimed towards writing about larger mainstream OS projects. Reviews (but not tutorials), benchmarks, research or statistics. Just my take, it's a little difficult to know, to be honest.