Oauth for email is part of the various RFCs pertaining to email authentication and has been around for years.
Thunderbird and various mobile apps support Gmail just fine using Oauth. I think the bigger problem is that many desktop apps seem to have stopped implementing changes to IMAP and SMTP about ten years ago.
If you have an email app that's no longer maintained, use app passwords (generated per-app passwords), like Google is indicating in the linked article. Those will still work. It's just the hardcoded username/password for the main account that's going away.
This will be a major pain for the Office 2016 users, as 30 september is still about nine months before their Outlook goes out of support, but for most users this will be quite a easy fix.