IMO if you develop a good understanding of Paxos then learn TLA+ you'll know everything you need to work on production distributed systems. Learn about CRDTs too, just to see what eventually-consistent systems look like. The real core of distributed systems is less knowing specific algorithms and more knowing what makes the field so hard, what solutions are possible, and the limitations of those solutions.

For learning Paxos I like this video: https://m.youtube.com/watch?v=JEpsBg0AO6o

Implement it yourself in your language of choice.

For TLA+ there's the Practical TLA+ textbook or Leslie Lamport's video lecture series: https://lamport.azurewebsites.net/video/videos.html