You will always need an origin for the redirect, as long as the spec doesn’t support other OAuth flows. For native apps that is obviously a hurdle, and we should probably discuss adding at least one more native-friendly flow to the spec.
That said, it’s possible to do, as the origin can be anything as long as it works as an HTTP redirect on that device (Chrome extensions/apps e.g. give you sth like chrome-extension://mjkkicfcbdoikeopenhhglbhdkcmpjhm/index.html. Not sure what you’re doing exactly with Chromium, though).
For advanced users (and others probably shouldn’t use a browser at this point, because most data is raw app data that can’t be opened in desktop apps) it might make sense to just make the token configurable for now, so they can use their own. That way you can develop the actual app instead of being blocked by the auth.
I can’t speak for others, but at 5apps we’ll soon launch a feature, where you can create new auth tokens directly from the storage dashboard (similar to what GitHub does with “Personal Access Tokens”). It is meant for developers and advanced users, so you can authorize e.g. backup/import/etc scripts without a redirect.