Recently Jan-Lukas Else wrote "How should I upload files to my Micropub media endpoint?", which is a question I myself have asked in the past.
Since having the ability to upload to my own media endpoint, I've found it has been a bit of a pain point to upload files without needing to create a post. For instance, uploading a screenshot to send someone, or upload an image for a post's featured image, neither of which flow expect a post to be created there and then, but to be consumed by other means.
On mobile, the great Indigenous for Android allows you to upload arbitrary files to the media endpoint, but there didn't seem to be anything on non-mobile platforms.
I am quite fortunate that my solution for my media endpoint is backed by a Git repo, so I can simply check it out, and
git commit my file, but I know others may not have this convenience, as Jan-Lukas mentions.
To fill the gap with this, I've just launched Micropub Media Endpoint Proxy, which makes it possible to upload a file to your media endpoint.
I've decided to go for a minimum viable product, and require users to provide their own access token, and their media endpoint URL - I'd be happy for someone to contribute the changes required for it!