IMPORTANT: These binaries are provided by anyone who are willing to build and submit them, they are NOT official. Because these binaries generally not reproducible, authenticity cannot be guaranteed. For your consideration, each download page lists the GitHub user that submitted those binaries.
ungoogled-chromium's GitHub page
Page source code and contribution instructions
NOTE FOR LINUX USERS: Make sure to download packages for the correct system. Portable Linux build works on any Linux platform supported by Chromium.