OneDrive for Business/Education
Suggestion
I suggest that Deja Dup add support for Microsoft OneDrive for business and education. As far as I'm aware, it's only working for personal. (#158 (closed)). Google Drive is ending its unlimited storage for education, and many institutions are now providing large quotas on and recommending OneDrive as a cloud backend (for example CU Boulder https://oit.colorado.edu/services/file-transfer-storage-infrastructure).
I don't understand the details, but another open source project (https://github.com/abraunegg/onedrive) is under active development and can synchronize a business/education OneDrive folder to a Linux machine with a relatively simple setup. That implementation does not work well for my purpose of backing up a machine, but perhaps this project could learn from their authentication technique.
There are a few older (~2017) posts online about how to get Duplicity/Deja Dup working with One-Drive, but they are all relatively involved and it's not clear whether they work, especially with business/education. Separately, if anybody is aware of a somewhat clean and verified way for me to make this work on my own, please let me know.