Hello.

First I understand that this isn't really an issue but more a question on my part as to how to go about implementing a specific flag on a packwiz backed Prism/MultiMC instance.

For context, we use a Gate Reverse Proxy service for our Minecraft Servers. Unfortunately, owo's handshake doesn't work with Gate. There is a workaround to disable the handshake, as given here: System Properties.

That said, I have been unable to determine how to implement this on a Prism/MultiMC setup. I know Prism instances are capable of this as we are able to use official modpacks like RLCraft and Cobblemon without issue on our Gate Proxy, but I cannot find where the property is set. It's not under Java arguments or environmental variables. I was wondering if anyone here would be able to walk me through how to set this up for Prism specifically.

If this isn't something you can do, I appreciate your time regardless.

On the latest versions of owo-lib the Handshake procedure should be disabled. From that I assume you are playing some very specific version, like 1.20.1.

For a Packwiz + Prism instance you should just be able to specify the argument in the JVM arguments before exporting the profile, as in the provided image:

Note that this also has to be correctly configured (disabled) on the server, as when handshake is required it validates on both ends.