The Meteor MySQL package has been around since 2015 and fully supports pub/sub and DDP using the MySQL binary log as the event source.
The most recent update was version 1.2.12 released on April 30th 2020 (21 days ago).
Over these years, I have personally known 6 Australian businesses who have relied on this package in their Meteor production apps, 5 of them not even running MongoDB.
Scalability has been at the heart of its implementation and I have even pushed for Meteor’s Mongo package and redis-oplog to be enhanced by incorporating functionality present in the MySQL package.
The Meteor MySQL package has been posted about many times in this forum and it’s frustrating to have to deal with the chronic amnesia I have seen in this thread.