Brave Browser shows horizontal lines on Youtube videos only when the timeline scrubber is visible. When timeline scrubber is hidden the lines disappear. Disabling add-ons had no effect. Disabling Hardware Acceleration had no effect either. This issue does not appear on other browsers, like Chrome.
On [Version 1.11.97 Chromium: 84.0.4147.89 (Official Build) (64-bit.