The only "ads" you get will be the ones the video uploaders encode directly into the video itself. Plus you can watch using whatever playback software works best on your system, instead of the rather feature free JS player youtube provides.
This is the only way to enjoy youtube without a premium account, and even with a premium account it's still far better to use a proper player like mpv.
But it seems likely to me that YouTube will eventually start embedding the ads more inextricably into the video streams while downloaded. Especially as more people use tools like youtube-dl/yt-dlp to circumvent ads.
They'd have to vary the ad timing to get past sponsorblock, and generating a video for each viewer to do targeting. I can't imagine Google going back to content-based ads after all this time.
https://github.com/yt-dlp/yt-dlp
The only "ads" you get will be the ones the video uploaders encode directly into the video itself. Plus you can watch using whatever playback software works best on your system, instead of the rather feature free JS player youtube provides.