Google is looking at server-side ad injections that some ad blockers might be unable to stop. Google is already testing the new ads, as some YouTube users have started spotting unskippable black segments of video that do not show anything.
Just opened a YouTube video and was met with 6 seconds of unskippable nothingness (most likely an ad that was blocked by ublock origin), this seems to suggest that they'll now inject the ads directly into the video stream.
As Android Police noticed, Google posted an update on the YouTube community pages about extensions on YouTube the same day the Redditors started spotting the new unskippable ads.
[
Collection
]
[
|
...
]