1. A genuine (?) Safari bug with the CompressionStream API. (we never learn what the actual bug was, and their bugreport to WebKit was literally just that "hey, our website at URL ... doesn't work" - no minimal reproducible example whatsoever. Lol)
2. An issue due to them relying on a Chromium bug.
3. An issue due to them assuming that OffscreenCanvas will always support both 2D and 3D (WebGL) contexts.