Hi, and welcome…!
I’m replying from the angle of a blogger who does both short content and longer posts. I believe you’re right, the Discover only shows the short micro posts. Technically, I think it’s possible to include long posts’ summaries (which you can do when writing a long post), but I don’t think I’ve seen those.
I think the intention with Discover and the feed is to imitate what other social platforms do (Twitter when Micr.blog started, Bluesky, Mastodon, etc.) and provide that familiar feel on purpose. Long posts, even with a summary, might not fit into those short, quick bursts of communication.
I don’t know if I agree that long posts are “second citizens.” I can see why it may look this way, but we have a lot of features on the platform that are meant to help and increase the experience of writing long-form posts - the categories, pages that work with RSS feeds from other sites (on my blog, my reviews of movies - which are long form - are automatically added), the capabilities of summaries, categories, a place to upload pictures and include them embeded in the post with descriptions, and of course plenty of plugins and themes built around the blogs. Sure, all of those exist on other platforms for long form too, and I do think MB can do better in terms of promoting long-form posts in a way - still, MB is unique in that it offers both.
All of that said, it doesn’t help you to find long-form post blogs, which is one of the reasons you’re here, so maybe I can be a bit more helpful with some tips that helped me along the way.
First, plenty of folks on Discover who write short posts also write long posts. If you follow them, you should see the long-form posts as well (summaries or just the first paragraphs on the feed).
Second is definitely word of mouth. Some folks (myself included) have blogrolls on their blogs; at other times, you tune in on a “conversation” in the feed, and those are usually comments to long-form posts, where people discuss things more at length.
Then there are carrorated lists outside of MB, usually aimed at RSS readers (RSS is the way to follow these blogs, and MB now offers a built-in reader, Inkwell). I often save those articles with MB’s bookmarks to respond later, which also helps.
I hope some of this helps. What do you usually like to read? Maybe I can suggest something, or someone else can. The community here is definitely helpful with these sorts of things 