I just installed an upgrade from LR 5.x to Lightroom 6 (not CC). Unlike other people who seem to have a problem with Lightroom 6 crashing on startup, the application works fine for me, except that it immediately crashes every time I try to open the Preferences dialog.
It does not matter if I try to access the preferences using the Cmd-, shortcut or through the Lightroom → Preferences menu item. There is an immediate crash every time.
Not that I have any urgent need to change any preferences—I just wanted to check if any preferences that might be new to Lightroom 6 needed adjustment.
It is on a MacBook Air running Yosemite 10.10.3.
I have this same problem, on a late 2013 MacBook Pro running Yosemite. Crashes in libGL.dylib, so it's related to hardware acceleration. The sad thing is I can't turn hardware acceleration off without opening preferences.
i just had a tech support guy remotely control my computer. He says he fixed it by holding on to alt(option) and shift while launching LR and then resetting preferences. Crashing was definitely tied to my trying to use hardware acceleration on my laptop. I'm disappointed that my fairly new macbook pro does not seem to be supported. At any rate, I haven't tried this fix so much as watched the tech support guy do it remotely, but that's what he claims allowed me to access my preferences again. The problem does come back if I try to fiddle with hardware video card settings, though.