When YouTube started taking advantage of iOS 14's picture-in-picture (PIP) functionality, it was limited to users with a YouTube Premium subscription. But now, the company is allowing all iOS 14 users who use the YouTube mobile website to access the feature, at least through Safari. The native YouTube app has never supported PIP, even for those with Premium accounts. But we'll keep you posted if things change. Apps like Netflix have already started offering the feature, so we're waiting for YouTube to cave.
Source: Engadget