I tried several of them, and so far I like Habla the best. They're all a bit "wonky" but Habla seems to provide the best set of features for markdown authoring, IMHO.

Encourage you to share your content! I think that long-form content in particular is one of the most promising ways that Nostr disrupts existing platforms, particularly Substack. I do find the latter to be a very valuable source of essays, but you can "smell the Xitter" starting to leak in with its new "social" features.