I use rsync frequently to send files to libreelec boxes.
The problem is rsync is installed to:
/storage/.kodi/addons/virtual.network-tools/bin
So I always have to run rsync from the client with this parameter:
--rsync-path=/storage/.kodi/addons/virtual.network-tools/bin/rsync
It's ugly and painful.
I know I can also change /storage/.cache/services/sshd.conf to configure sshd to allow overriding the PATH environment variable, then setting it in the client, but this is also ugly and painful.
So I propose 2 possible solutions:
1. include rsync in LibreELEC proper (instead of an addon), put it in /usr/bin.
2. symbolic link: /usr/bin/rsync -> /storage/.kodi/addons/virtual.network-tools/bin/rsync