how to compile own libreelec image?

Unti now, my selfhosting experience did not need any compiling, but for my current goal I need a custom Libreelec image, because I wish to use systemd-journald-remote and play around wit virt-mgr and spice. (running on a Proxmox) What is needed for compiling my own Libreelec and have it up to date along the usual Libreelec publish?