Mac OS 10.11 El Capitan’s now been out for a day or so, and you may be wondering whether it’s safe to upgrade.
As far as Lightroom goes, there are a couple of issues under investigation so far.
The big one – Nikon and Leica tethering is not working.
Update 2016-01-27 – Nikon tethering is fixed in Lightroom 2015.4 / 6.4. Leica tethering is still waiting on an update from Leica.
It also appears that there’s a problem with LUT monitor profiles, although smaller Matrix profiles are working as expected.
Some people (including Peter in the comments) are seeing a permissions problem for new Lightroom installations, which can be fixed using step 6 in this tech note.
Adobe also now have their own tech note.
I’ll add to this list as I hear of additional problems.
There’s a thread at MacRumors with a list of other software known to be working or not working.