Currently there aren’t too many tools that are native writing onchain tools. The biggest one right now is Paragraph.xyz. As of early May 2024, Paragraphy has acquired Mirror.xyz which was another platform that supported newsletters or longer form writing onchain but for now this is the biggest.
Paragraph | all-in-one publishing & newsletter platform
Micro Blogging or short form writing can be done in many places. The current main method of onchain writing uses the Farcaster protocol. There are many apps/clients that support this protocol.
Gramajo (@gramajo.eth) on Farcaster
As an example you can see below, of the above link toward the bottom you can access Farcaster with Warpcast, Supercast, Firefly, Yup, Nook, Buttrfly and more.