Can confirm - Grammarly is awesome! Didn't know about Hemingway Editor - will check it out. As for Forest - I can't speak for mobile, but on desktop, I prefer something a bit "tougher" - Cold Turkey
Also, as a shameless plug, I've created a tool ( browser extension ) exactly for this purpose - CodeWrite - blogging tool for developers.
It has a WYSIWYG editor with Markdown shortcuts, integrates well with Grammarly, has a built-in code editor and formatter, and "auto-fills" (cross-posts) your blog post on Hashnode, Medium, and Dev.to while automatically handling incompatibilities. It has premium plans (as cheap as $3/month), but you can use it for free within certain limits, so check it out if you're interested!