This project was a huge pain that involved a lot of learning. I wanted to use Unity's new Netcode solution, that was still in beta, which was a huge mistake. The lack of documentation made it so hard to get anything working. In the end I only barely got online multiplayer working and it's only within a local network. I learned a lot but I won't be using the new Netcode solution again until it's well out of beta.
At least I accomplished my goal of learning a lot more about networked multiplayer.