I believe I have found the solution for HLS: In Safari > Advanced > Experimental WebKit Features, enable the following GPU Process: Canvas Rendering GPU Process: Media GPU Process: Video Capture GPU Process: WebGL WebGL via Metal Note: Unfortunately, this does not solve loading standard mp4 files in Safari. The load time is still over 10+ seconds before visually rendering

Just a reminder to Apple that this issue is NOT resolved in iPadOS 15.1 Beta 2.