I have found exactly the same - some of the Mongoose and Joi syntax has changed and has needed a bit of research, but overall I still think the course is great.
Regarding transactions, Fawn is outdated and doesn’t seem to work with the latest version of MongoDB anyway. After a lot of research, I have concluded exactly the same as this post: [Mongoose] Transactions vs Fawn (Two Phase Commits) - #7 by mandatoryUserName
TL;DR you need a replica set in order to use transactions. Personally I decided life was too short and carried on with the rest of the course! Transactions and replica sets will be for future me if necessary…