OMG, this thing indeed works! At least for outlook.com it does.
Client ID and client secret can be snatched from FairMail here: https://github.com/M66B/FairEmail/blob/master/app/src/main/res/xml/providers.xml
Oh, and it only accepts unencrypted connections to itself — it's supposed to run on the same machine, shouldn't be a problem, but you have to set sslproto to '' in .fetchmailrc to force it.