Steps to reproduce:
Visit the URL http://the-edge.taht.net/post/bending_the_rules/ with compatibility mode turned off in Orion, which will cause the browser to download a zero byte file named "kZx_TokIHdI". This is the video ID of youtube dot com/watch?v=kZx_TokIHdI, referenced with an iframe in the page source. Turning off Intelligent Tracking Prevention will allow the embedded video player to appear normally.
The embedded video player should appear normally, and no empty file should be downloaded. (Safari 14.1.2 has no issues viewing the video as intended, and it works well in a Chromium test with Vivaldi 5.0.2497.32 as well. AdGuard was used in my test on Safari with ITP turned on, and uBlock Origin was handling content blocking in Vivaldi. The built-in content blocker was used in Orion, and my only active extension is Bitwarden.)
Orion, OS version; hardware type:
Orion version 0.99.109.1-beta on macOS Mojave 10.14.6 (18G9323)