If you're willing to slog through the command line and your own support, then a copy of the Snow Leopard installer and an installation of VirtualBox might get you where you want: mac - Install macOS High Sierra as VirtualBox guest (on macOS High Sierra)? - Ask Different As an approach distinct from an app-level emulator, virtual machines are available for High Sierra and Mojave running on a Mac, and various of those packages can install and boot and run Mac OS X 10.6 and its apps as a guest.
