How to "release" a subnet outside in mikrotik?

Question

network hardware

raised an OpenVPN server on the mikrotik router (subnet 172.21.108.2), you need clients to go online. Plus, so that pings go to clients on the internal subnet (192.168.88.1)

Answer 1

Initially lied. I am correcting myself.
Everything should work right out of the box. For VPN, you may need a NAT rule towards the Internet.
What's wrong? Ping from the client to VPN, from VPN to the Internet and from VPN to the network.

Answer 2

It looks like you didn't pass the correct routes to your openvpn users.
They ping the external address along the default route.
Check routes with clients.

Answer 3

I'm not sure, but try in the profile used by the OVPN server, set the bridge on which the LAN clients "sit" (by default, bridge-local). Change ARP from enabled to proxy-arp in the bridge settings.
A very simple option is to "hardcode" the route to the local network in the user's OpenVPN profile.