With many VPN providers dropping support for anything but OpenVPN and WireGuard, I googled 'V2860 OpenVPN' and came up with a V2860 Series manual which gives instructions for configuring OpenVPN. However, I cannot find the stated menu entry for OpenVPN on my V2860Vn+, running 3.8.9.7.

Is there a possibility of setting up OpenVPN on my V2860Vn+? Is there an alternative firmware?

Did you get anywhere with this ? My VPN provider has just dropped support for anything other than it's own client or OpenVPN and my L2TP connection has just stopped working.

Time to either find a new VPN provider or a new router that supports OpenVPN.