I noticed that LibreELEC has a VNC server for Raspberry Pi, but there is no VNC client in the repository. (I typically use LibreELEC in a classroom environment to display videos from a networked file server — but sometimes I need it to mirror the screen of the instructors desktop PC.)
DirectVNC is a client implementing the remote framebuffer protocol (rfb) which is used by VNC servers. If a VNC server is running on a machine you can connect to it using this client and have the contents of its display shown on your screen. Keyboard and mouse events are sent to the server, so you can basically control a VNC server remotely. There are servers (and other clients) freely available for all operating systems.
What makes DirectVNC different from other unix VNC clients is that it uses the linux framebuffer device through the DirectFB library which enables it to run on anything that has a framebuffer without the need for a running X server. This includes embedded devices. DirectFB even uses acceleration features of certain graphics cards. Thus a lot of configuration can be done by creating the library specific configuration file /etc/directfbrc or the program-specific configuration file /etc/directfbrc.directvnc. See directfbrc