Unity 2017 -> 2018 is an external nightmare

Short story:
Unity team, add a message to your 2018 installation telling people that they need to update Visual Studio in order for Unity 2018 to work! The message "The solution file could not be loaded because it was not found" isn't user-friendly nor informative (how can we guess it's because of an outdated VS version?)
Also: Android SDK doesn't work with Unity anymore?

Long story:
I love Unity and decided to update to Unity 2018, hoping for a smooth transition and improved workflow. The transition was everything but smooth.
The moment I opened one of my 2017 projects in 2018, the console got sprayed with tens of warnings regarding the package manager. Note that it was a simple project that imported no extra packages.
When I used the package manager to delete Unity In App Purchasing (which I didn't ever use so I felt free to delete) the console threw a bunch of errors and refused to compile my code until I re-installed that (unused!) package.
When I created a blank new project and added a new script, I discovered that Unity hasn't generated a solution file to my project!
After some research I figured I should update Visual Studio as well.
Later, when I tried to build one of my Android games, Unity claimed that I have Android SDK version 0.0.0 (!?) and refused to build. Updating the SDK didn't work. Deleting and re-installing the SDK didn't work. Manually updating Unity's SDK path didn't work. Now I can't build my app.

 

I have only good experiences from Unity 2018. It builds fine to Android (on Mac OS 10.12).
Is your Android Studio up to date?