No, this is not needed. Online video streaming nowadays uses a "playlist" of video chunks. These chunks are seperately encoded videos, so can easily be swapped out, or concatted to. This also means that an ad-blocker could ignore specific chunks if they know which ones to ignore.
No, if YouTube displays any UI such as a clickable link, that means it has to know how long the ad is. SponsorBlock could find this data as well. There is also the feature for clicking on a timestamp in a comment that would need to know the duration of the ad, so it should be findable somewhere, it just might be kind of hard.
In the short term, SponsorBlock will not work for people with this experiment.
Probably not. But it makes things harder. As always, uBlock Origin work best on Firefox-based browsers, especially now that we reach the end of manifest v2.
Maybe in the future, but at the moment it seems to only switch to this server-side ad injection via client-side flags.
The more pressing issue for these clients is the new sign in requirement to watch videos for some people.
The offsetting issue will affect DeArrow thumbnail submissions, but should be fixable in the same way as SponsorBlock.
My thought is that if you're willing to spend actual money to remove adds, installing Sponsorblock is an easy sell, since it cleans the rest of the ads up.
If they don't re-encode, then theoretically all you have to do is crc check the encoded video at every resolution/format against a database of ads. But it would require somehow finding out where the playlist segments start and stop. If there's a button to click which becomes available during an ad, we know that it's an advertisement up to a specific point in time.
That way, as soon as the database confirms the first segment is an ad (and how long/ how many there are after it - information also within the database) you can just skip ahead to the content. Since there are many users, a ton of data could be flowing in and have it working decently within a few hours.
I cannot get YouTube to give me the new server-side ad experience, so I can't do any preliminary testing. @ajayyy have you actually seen these ads yourself yet?