OpenVPN - Client to Client LAN access

Hi!
I have already read this topic solving the 50% of my issue.
My configuration is composed as for the attached picture. The goal consists in reaching the IP Camera in the OpenVPN client’s LAN from another client (for example by a smartphone).
I have followed all the steps described by @dengxinfa (replacing obviously the LAN client’s ip address with 192.168.20.0) and now I’m able to access to the IP camera with my laptop connected directly to the OpenVPN server.
I’ve read the official guide of the OpenVPN community where are explained all the steps to configure the client’s LAN access between clients. The procedure is similar/equivalent to the @dengxinfa’s, I have only added also the statement --push “route 192.168.20.0 255.255.255.0” under --client-config-dir “/etc/openvpn/client_config_dir” \in the /lib/netifd/proto/ovpnserver.sh file.
Client-to-client switch is turned-on in the GL-MT300N-V2 Server OpenVPN.
Allow access to LAN is turned on in the GL-MT300N-V2 OpenVPN client.
When I enable the OpenVPN client in my smartphone and I type the OpenVPN IP address 10.8.0.2 in the web browser, I’m able to access to the main page of the GL-MT300N-V2 client. 192.168.20.x IP addresseses are instead not reachable.
Probably I have only to configure correctly the additional route in the server, but due to my little experience/knowledge I’m not understanding in which way to proceed.
Thank you in advance for the (possible) suggestions!