The deployment methods are somewhat different too. With dokku, you need to add a new origin to your local repo and push to that origin whenever you want to deploy, Heroku a-like. For Coolify, you have an option to deploy on push via a webhook like Vercel or Fly.io
As the Dokku maintainer said in another comment it is possible to deploy directly from an image instead of from a repo.
For one of my project I build and store the image on GitHub and deploy it on Dokku.