Rather than ask the question "How do I upload a video to a streams Channel," the better question would be, "How do I get other people to see a video I want to upload?"
Before, those people you wanted to see it would have to go to a special video-only portal to look for it, and find your channel among all the other channels, and then find it among the videos you've uploaded to the channels. If you wanted to display your video on SharePoint, you had to use a special web part. If you wanted to share it outside the company, you couldn't.
Now, with Stream (on SharePoint), you'll upload the video to a spot in OneDrive or SharePoint Online that makes sense for the content of the video. If it's about cats, and you want to share it with a few people, maybe you'll upload it to a folder in your OneDrive named Cats and share it with them from there. If it's about dogs, and you want to share it with lots and lots of people, maybe you'll upload it to a Communication site about Dogs. If it's important to a group of people you work with, then maybe you'll upload it to a channel in a Microsoft Team (which will sit in SharePoint). Regardless of storage location, you can manage the permissions and sharing on it just like any of the other files you upload or create. If you want to share it outside the company, you might be able to do so (provided your company's tenant allows for the location where you stored it).
And if you want to display it on a SharePoint page, you don't have to use a special video-only web part anymore. You can use several regular SharePoint web parts such as Highlighted Content, File and Media, or even the Hero.
https://support.microsoft.com/en-us/office/using-videos-on-sharepoint-pages-5a0eb37c-81a8-45b7-875e-...As to that massive pot of chaos, can't really help you there.
🙂
