Yes. In Performance Max assets and in the Create campaign wizard (Display and Demand Gen), click Upload video from computer. The file (MP4, MOV, or WEBM, up to 256 MB) goes through Ads Editor directly to Google Ads, which publishes the video as unlisted on a Google-managed YouTube channel linked to your ad account.

You don't need to connect YouTube or have a channel. The video takes from a few seconds to a few minutes to process, and once it's ready, you can add it to the ad.

The video does not appear on your channel (or your client's): it stays on that Google channel, only for ads. Publishing to the client's own channel is not possible through Ads Editor: the connected person would need upload permission on that channel, and Google's API doesn't say which channels they can use. If the video is already on the client's YouTube channel, you can paste its link in the Performance Max assets.

Video (YouTube) campaigns themselves can't be created in Ads Editor, because Google's API doesn't allow it. For video with a conversion goal, use Demand Gen.