...The promise here is to let you choose, for example, any reverse proxy you want or any database you want, without requiring work from maintainers of the services you want to self-host. To achieve all this, SHB is using the full power of NixOS modules and NixOS VM tests. Indeed, each building block and each service is a NixOS module using modules defined in Nixpkgs and they are tested using full VMs on every commit.