How to add a Windows Firewall rule to enable client-to-client communication through OpenVPN

Open PowerShell with Administrator Privileges and type:
check the path to your openvpn.exe!

New-NetFirewallRule -DisplayName “OpenVPN allow Inbound” -Direction Inbound -Program %ProgramFiles%\OpenVPN\bin\openvpn.exe -RemoteAddress LocalSubnet -Action Allow
New-NetFirewallRule -DisplayName “OpenVPN allow Outbound” -Direction Outbound -Program %ProgramFiles%\OpenVPN\bin\openvpn.exe -RemoteAddress LocalSubnet -Action Allow
Set-NetFirewallProfile Public -DefaultInboundAction Allow -DefaultOutboundAction Allow

from now every connected client should be able to ping you

Optional: To see if it has been added open Windows Defender Firewall: wf.msc.

that's all
Have a nice day