Email isn’t “the only way” to send patches. In fact, he addresses that:

It doesn’t have to be by email, either. Any method of sending this data to the maintainer is fine. For example, I’m on Mastodon – so you could send me a repository URL via Mastodon if you really wanted to (provided you didn’t mind my responses being very short). Or you could send patches via any other communications medium that you and the maintainer are both on, if it lets you attach files to messages.

His preferred method is just sending a URL over email. You can use any communication method if you both already have an account.

I remember the DS had a similar feature. You could connect to people nearby and they could download the game and play with you. It was super cool, and I hope this becomes more common.