We have a few intrepid users self-hosting the entire Firezone stack, but we don't have documentation to support it (yet), and wouldn't recommend it for production. It's something we'd like to write and maintain eventually, even if only for smaller / hobby deployments.
We do have a self-hosted community support channel on Discord if you are feeling adventurous: https://discord.gg/DY8gxpSgep
I would recommend starting here with a local development cluster:
https://github.com/firezone/firezone/blob/main/docs/CONTRIBU...