I installed Tizen SDK 2.3.1 via web installer on my Mac Book Pro with OS X El Capitan, but IDE looks like normal eclipse.

I found in ‘Help’ > ‘Install New Software…’ > ‘”Available Software Sites”‘ two entries:

• file://Users/MY_USERNAME/tizen-sdk/ide/updatablenative
• file://Users/MY_USERNAME/tizen-sdk/ide/updatableweb

but these folders do not exist. Maybe that’s why the Tizen plugins cannot be installed. 

‘Help’ > ‘Check for Updates’ needs some time, but it has no results.

EDIT: I tried to install via sdk image, but still have the same problem.