Setup VPN Bridge to HMI Device

Please refer to below representation of what I am trying to achieve.

         +----------+
        +            +
    +--+   openVPN    +--+
    |   +            +   |
    |    +----------+    |
    |     10.10.10.x     |
    |                    |
    |                    |
    |                    |
    |                    |    
+--------+           +--------+          +--------------------+
|        |           |        | ETHERNET |                    |  
|  RPC1  |           |  RPC2  |----------|  HMI/PLC DEVICE    |
|        |           |        |          |                    |
+--------+           +--------+          +--------------------+
10.10.10.2           10.10.10.3                10.10.10.4

RPC1 : Windows based PC running OpenVPN Client
RPC2 : Linux based server running OpenVPN Client
openVPN : VPN Server running on cloud (internet) providing VPN connection between RPC1 and RPC2.
HMI/PLC DEVICE : An HMI/PLC device. It has Ethernet Port and can be setup with static IP address

Currently, via the openVPN server, RPC1 with IP 10.10.10.2 and RPC2 with IP 10.10.10.3 talk to each other as they are now part of same subnet.

What I am trying to accomplish is to have the HMI/PLC device also be on the same VPN so that it can be accessed from RPC1. I have given it an IP of 10.10.10.4, but cannot install any VPN client on it.

So, the ask is, what needs to be done to setup some sort of routing/tunneling/network setup on RPC2 so that HMI/PLC device becomes part of the VPN? The traffic is both UDP and TCP.

Thank You.