This is my take on a ruby devcontainer. The Microsoft one includes a couple deprecated extensions that can't be removed easily. In addition, I wanted some other options for ruby versions and build tools.
devcontainer.json
{
"name": "Ruby",
// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
"image": "ghcr.io/mattcburns/devcontainer-ruby:latest"
// Features to add to the dev container. More info: https://containers.dev/features.
// "features": {},
// Use 'forwardPorts' to make a list of ports inside the container available locally.
// "forwardPorts": [],
// Use 'postCreateCommand' to run commands after the container is created.
// "postCreateCommand": "ruby --version",
// Configure tool-specific properties.
// "customizations": {},
// Uncomment to connect as root instead. More info: https://aka.ms/dev-containers-non-root.
// "remoteUser": "root"
}