Found it. It had nothing to do with the PWA or Swydo ddp-apollo! I just hadn’t noticed the server console log error message before.
I’d just recently added in an Apollo useSubscription hook. The subscription was working.
In the hook, I was using:
variables: {"localUserId": Meteor.userId()},
When Meteor.userId() was null and the hook ran, I got the error shown above. It was a type error and had nothing to do with PWA or Swydo ddp-apollo. 