The official versions on Steam and Itch.io automatically update to the latest build (currently beyond v1.2.1). If you are looking for this specific version for "down-patching" or speedrunning purposes, community forums often provide guides on how to access older manifests.
Many searches for specific ZIP files come from players looking for mod compatibility. The Lunacid modding scene (available via Nexus Mods) is very active, and certain older mods require specific versions like v1.2.1 to function correctly. Security Warning file lunacidv121zip hot
Here is a deep dive into why this version is in high demand and how to navigate the community around it. What is Lunacid? The official versions on Steam and Itch