CyanogenMod has long been the most popular custom ROM, covering a wide array of devices from numerous manufacturers. But after the breakup of Cyanogen Inc, and the subsequent end of the company's support of CM, LineageOS was formed as a continuation of the project. Now LineageOS is preparing to offer official builds for over eighty devices.
A new blog post on the LineageOS site has announced that builds for "Marshmallow and Nougat capable devices" (likely meaning devices that received official CM13 and CM14.1 builds) will start this weekend. LineageOS release candidates will be released every week by default, and are signed with a private key for authentication and signature control.
In contrast to CyanogenMod, LineageOS will not allow root by default. Should you want root, an optional flashable zip will be provided by the project that will root the system, and you will only need to flash it once. If you're compiling the ROM yourself, you can use a switch to include root.
Switching ROMs can often be a pain, forcing you to lose all your app data and settings. To help alleviate this problem, LineageOS will offer experimental data migration builds along with weekly release candidates for the next two months. These builds can be flashed on top of existing CM 13 or CM 14.1 installations, keeping all user data intact. Once you are running the data migration build, you can freely switch to normal LineageOS builds.
It's a good idea to start custom ROMs with a clean slate, but if you really don't want to set everything up again, the migration builds are very handy. Keep an eye out on the LineageOS downloads page for builds this weekend.