Google is introducing automatic linking between YouTube channels and Google Ads accounts when strong data signals show they belong together. Admins and channel owners will get an email 30 days before the link is created, with the option to opt out or link early.

Once linked, advertisers can use YouTube audience data-like views, engagements, and interaction-based segments, to improve targeting and campaign performance.
The link doesn’t grant control over the other account, and personalized-ads settings still limit available data. You can unlink the accounts anytime or manually link them later if you opted out.
Read the full update spotted by Hana Kobzová here: About automatically linked YouTube channels and Google Ads accounts