This repository builds and publishes Docker images tailored for use with nektos/act, a tool that runs GitHub Actions locally. The images are based on Ubuntu (22.04, 24.04, 26.04) and come in multiple variants: a base 'act' image, a 'runner' image with a non-root user, and flavour images that add specific toolchains (JavaScript, Go, Rust, .NET, Java, PowerShell, GitHub CLI, and a custom combination). The build process uses buildah for multi-architecture (amd64, arm64) container builds and pushes the resulting images to GitHub Container Registry and Docker Hub. The repository also includes a workflow to copy full runner images from an external source and re-tag them. The architecture is a set of shell scripts and Dockerfiles orchestrated by GitHub Actions workflows. The main entry point is the build-ubuntu.yml workflow, which triggers on schedule, push, or pull request. It uses a PowerShell script (build.ps1) to invoke buildah with manifest-based multi-arch builds. Installation scripts for each flavour are located under linux/ubuntu/scripts/ and are sourced by the Dockerfile. Helper scripts in linux/ubuntu/scripts/helpers/ provide reusable functions for environment variable management, download with retries, checksum verification, and OS version detection. The codebase is actively maintained (last commit within days, regular scheduled builds) and shows low technical drift. Dependencies are kept current through automated downloads of latest tool versions. The helper scripts are well-isolated and could be extracted for use in other container build projects. The overall quality is solid, with clean separation of concerns and robust error handling in the build pipeline.