I recently bought a PineTab2. Its a pretty rough around the edges experience (hardware is fine, but Plasma Mobile is still lacking compared to Android) BUT with the case with a keyboard it is far better for writing anything. Not as good as my desktop, but a lot better than most mobile devices.

I usually use Whatsapp web and the Signal desktop app at my desktop when I want to write more than sentence or two. A physical keyboard makes it so much easier. For example, I left making my comments here today until I sat down at my desktop.

If you must use a phone for typing more than a tiny bit, buy a keyboard for it. Even a little bluetooth keyboard is a lot better.

I am tempted by phones with keyboards. I used to have a Blackberry a long time ago and there are Android phones in similar formats.