Run live Linux in Ventoy without install screen

I want to do something really simple: make an ISO image that boots directly into Steam Big Picture with persistence. I know this kind of thing is possible because of Recalbox, which does something similar. I've been trying several distros, and all of them have the same issue: the live version can only be accessed after an annoying "try or install Linux" popup. Even in server versions of distros, there's often not even an option to run it in live mode. I can set up my own x server stuff to make this happen, so if there's a way to run a server Linux distro live without any install wizard, I could get this to work. I understand that stock SteamOS might do something similar, but SteamOS 2 is largely outdated now, and SteamOS 3 is not available as a separate distro (all the links to it currently point to the Steam Deck recovery image, even on the site that says "Not for Steam Deck"). I know there are tools like Linux Live Kit that would supposedly do this, but this needs to run on a Ventoy drive with multiple ISOs on it, so I cannot use their tool to fill up an entire drive. If anyone knows a distro that works like this, or how to disable the install script in existing distros, that would be appreciated.