UPDATE (Oct 16, 2018):
Since this post was published, there have been 5 more minor updates to Tizen Studio 2.x and a few weeks ago I was able to successfully get everything working on the current latest (version 2.5 released in August).
Based on early comments, we know 2.0-2.3 was broken, but likely 2.4 (released in May/June) might have worked too... but I never tried it so... ¯\_(ツ)_/¯
Any way, go ahead and give the newest Tizen Studio 2.x another try (following the official docs worked for me!)
(Original post is below)
TL;DR - In the Package Manager Configuration, turn "Auto Update" OFF and make sure 1.3 is the selected version. Then, manually add the TV Extensions 3.0 repository to the Extensions SDK.