I have previously noted my post composer is Obsidian; this has been going quite famously. I have a few quibbles with its tag handling--if I toggle from source mode to read mode it breaks out all of my tags in that post by spaces, which means I can't use it as a way to track what tags I have/haven't used before--but overall for a "force a thing to be my post composer" it has needed next to no assistance from a shoehorn to fit my purposes. I have posted more posts than I am willing to count, just in the few months I've had this up!
One of the things I love is using its template feature as a way to insert img html[1] and post metadata (including the important timestamp, automatically correctly formatted!) in each Post. I recently stumbled across the fact mobile Obsidian has a swipe-down-from-top gesture you can map. It's usually mapped to some undoubtedly-powerful-on-computer command palette but I have never used that once and I use templates every post so: bam pow I can now swipe from top to insert my things instead of hiding my keyboard to access a hamburger menu to access the template menu.
I continually threaten to actually canonicize some classes in my css for formatting these, and am forever not doing it. I have instead put all the formatting within a style tag in my templates for images 🤷 ↩︎