When searching the Flathub store for markdown editors, I found Folio, which works well for me. I use Syncthing fork to sync my notes folder between Android and Linux, and use https://apt.izzysoft.de/fdroid/index/apk/com.printnotes.printnotes on Android to edit it.
Why is the reply green like it’s from you, but the bubble is coming from the left side, which is their side, rather than your, right, side?