The battery life is still good, although I switched to a different phone in early 2017 and have only used the Meizu as a secondary handset since then.

It came with Ubuntu pre-installed. I believe that the pre-installed Ubuntu ones have an unlocked bootloader, so you can put whatever you want on it as long as it's compatible. I know that a few people got CyanogenMod working.

I currently have Android Flyme on it, which is the standard Meizu OS that comes with the normal version of the phone. It's really good, but I would say lacking in security. I use it as a 'dirty' phone, for connecting to public Wi-Fi and insecure stuff like that, so I don't have anything confidential or important on there, and I never sign-in to things in the browser or apps.