I like Plex except the authentication.
They're also designed to be confusing and to give a user the impression you have to sign up for Plex Pass to continue using Plex. Plex is awesome together with Chromecast anyway.
They've "streamlined" it to the point of unusability.
It also works with a Raspberry Pi client without authentication.
That version is open sourced (https://github.com/plexinc/roku-client-public). The Plex developers have abandoned it, for updating the newer client only; but it's still perfectly usable as the old-version.
source: I wrote skip-sign in, manual server entry in the core platform.