Microblog.pub is a lightweight privacy-friendly single user ActivityPub server with a minimalist interface, whose accounts can be followed from other ActivityPub platforms including Mastodon etc. The platform features both short form notes and long form articles, and supports markdown formatting.
You’ll need some technical knowledge to install it as it’s not yet available through managed hosting. There’s more info about it on the official microblog website ⧉ and if you are familiar with server software you can find installation instructions here ⧉.