I would say that most Discourse instances are self-hosted. It’s as good as you set it up, the software is amazing and almost without glitches so most of the issues are more on a reliability or keeping it up to date and working and that’s 100% on you.
You will need to setup or ponder if you need a CDN, external storage, latency of storage, CPU and RAM, etc. With the hosted version you have all that sorted out.