If the laptop and iPhone can connect the LibreELEC side of things is working fine. That means the issue is either Android (possible but IMHO unlikely) or the network (my guess).
Auto-discovery features normally use mDNS broadcast on the network (and LE supports this) but if you have multiple switches in a daisy-chain or bad config in a managed switch the broadcast traffic might not be forwarded. Another common mistake is having a wireless router plugged into a switch and not configured as a wireless bridge; meaning a NAT firewall runs between LAN and WLAN segments and the firewall blocks the traffic.
Describe the layout/devices of the network.