I’m using Unity 2020.2.1f1 and I cannot find ProBuilder under the packages.
ProBuilder was easily found in the 2019 version iirc, so what’s going on?
I had a similar problem trying to find ProGrid. I’m using 2019.4.21 and at the top of the Packages tab is a pull down menu named “Advanced”. I chose “Show Preview Packages” and I could finally see ProGrid.