Support for Hyperlinks
iOS 15 now supports Markdown in their Text views. Links shared via the share sheet now correctly render as a clickable link.
New Done Button to Close Keyboard
Previously you had to submit an empty note to get the keyboard to close or tap on the notes above. With the new support for hyperlinks this clashed with the ability to click a hyperlink. The new toolbar above the keyboard will eventually be expanded to include new (yet to be determined) functionality.