linuxserver/docker-baseimage-kasmvnc ? reverse-engineered prompt

Build me a Docker base image project for a web based Linux desktop using KasmVNC, something I can reuse as the foundation for other desktop apps and desktop environments.

I want it to work on a few common Linux distros, support both x86 and ARM, and let me run a desktop from the browser with audio, basic login protection, and optional Docker support inside the container. It should have a simple Openbox style desktop by default, use a home directory under /config for persistence, and expose a few easy environment variables so I can change the port, username, password, title, language, and whether it runs full screen or without window borders.

Please set it up so I can also drop in one app and have it launch automatically, and make sure the base image includes the helpers needed for persistent portable apps and file access. If anything needs current docs or best practices, look them up online and follow them.