Adobe has released (available as part of Adobe’s Creative Cloud Photography plan) with a new feature for Creative Cloud members. The Guided Upright tool enables Lightroom CC 2015.6 to straighten images, fix horizons, and reduce or eliminate the keystone effect in buildings (see this  from the Lightroom team for a brief tutorial).
Both Lightroom CC 2015.6 and the standalone Lightroom 6.6 ensure that Merge to Panorama and HDR work properly with Smart Previews, add a Pending Sync Activity to the mobile section of Lightroom Preferences, and fix numerous bugs. The apps gain lens profile support for over 60 lenses and add support for new cameras, including the Canon PowerShot G7 X Mark II, Leica M-D (Typ 262), Nikon Coolpix B700, and Panasonic DMC-GX85, plus these tethered cameras: Canon EOS-1D X Mark II, Canon EOS 80D, and Canon EOS 1300D/Canon Rebel T6. ($9.99 monthly subscription or $149 for the standalone app, free update,, 10.8+ for Lightroom CC 2015.6 and 10.9+ for standalone Lightroom 6.6)