I installed VS2019 when it was released, and have been enjoying using the new features; however, I've had nonstop issues with the Unity development extension not working. No matter how I open VS, I don't get the attach option. I've tried running as admin and opening the project from the Editor in Assets->Open C# Project. I've been forced to revert to using VS2017 multiple times. For what it's worth, my project is currently stuck in 5.6.6f2 (yeah, I know), but I have seen this same issue when working in the QA version that is now in 2018.3.1f1.