I'm going to throw out some quick thoughts here to maybe get you started. I'll come back and hopefully add some detail later.
I don't see this as being easy, but I do think it's possible. I haven't done an openvpn connection from inside WSL, but I think I can visualize the flow.
The hard part is that you are connecting the WSL2 (Hyper-V) virtual NIC to the VPN, so all traffic between WSL2 and the VPN endpoint is encrypted, giving the Windows NIC no way to tap into it (even though it is "hosting" the virtual network).
The good news is that there is a way to "tap into" the WSL network from Windows, albeit "hacky". Again, I'm just going to lay out the basics here of what I believe might work. I'll have to come back with more details later.
socat is a networking tool that allows you to redirect network traffic over a number of different link types. One of these links, interestingly enough, is stdio. I've successfully connected to WSL2 stdio with socat using the wsl command. (See "Option 3" in this answer).
My hope is that you could set up a proxy server in a WSL1 instance with a port mapped through stdio to socat running in the WSL2 instance. The Windows' browser would then connect to the proxy server and be able to tunnel out through the WSL2 VPN.
There's even a socat compiled for Windows that would probably simplify this even further, but I haven't tried that yet.
Like I said at the start -- Not exactly easy.
Out of time for the moment. Do you think this is a path you'd want to take?
