How to redirect incoming (to ProxyVM) TCP connection to local port using iptables?

ProxyVM (ubuntu 20.04) creates virtual interface for incoming connections from each VM connected. Like

vif11.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet  netmask  broadcast
        inet6 fe80::fcff:ffff:feff:ffff  prefixlen 64  scopeid 0x20<link>
        ether fe:ff:ff:ff:ff:ff  txqueuelen 32  (Ethernet)
        RX packets 2123  bytes 730737 (730.7 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 3263  bytes 2818605 (2.8 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

But all the connections just goes to eth0 (I guess…). Task is to redirect them in localhost:port.
I looked up gw-15 iptables rules for a clue, but didn’t understood a thing.
There’s a community guide on VPN setup, that includes some iptables rule management, but it covers only killswitch\failprotection and name servers setup. I can’t see normal redirection rules in it (probably cause openvpn service does it?).
There’s tinyproxy mention in gw-15 iptables rules (end of nat table), but that’s only a http(s) proxy, not a tcp.