Finally manage to install Iflix Apps in the Unifi IPTV box. It seems if you install the latest version, it somehow won't detect Unifi so it won't autologin using the 1 year free subscription. But if you install the older version of Iflix (I use Iflix 2.1.17.1), then it will detect. After that you could update.

Unfortunately, I can only update until Iflix 2.7.0-893. This is bcos if I install Iflix 2.8.0-1027 (nicer interface & more remote friendly), I can't play the video as a message pop-up stating need to confirm mobile number. Anybody has a work around for this?