Not everyone trusts DigitalOcean for their hosting.
There's certain to be one on AWS and likely other providers.
Bitnami hosted on AWS? Or a Bitnami image hosted on your own server?
I second this; while Dokku sounds like a great way to ship your own fleet of applications (Heroku style), I'm not sure I see any benefit in using it to deploy GitLab. There are already images working on the main cloud providers and it seems to me a bit overkill for something you'd update once every few months at best.
Also, Gitblit[0] if you want to run on your own machine.