Sites like Construct 3 host simplified, 2D, or top-down versions of Siege mechanics. These are often allowed by school or work filters because they are lightweight web apps rather than massive executable files.
Most links marketed as "unblocked Rainbow Six Siege" do not host the actual game. Instead, they typically offer one of two things:
If your school or office blocks gaming launchers (like Steam or Ubisoft Connect), these methods can help: