localStorage and portable version

[yo252yo]

Hi folks!
I'd love to use ungoogled-chromium to distribute a web browser game that I'm working on (https://yo252yo.itch.io/rensdemo) on distribution platforms that demand a standalone executable (steam...). The portable version in the binary download works really well, but localStorage seems to be getting reset between each use, preventing me from remembering anything. My understanding is that it relies on temp files that get deleted immediately. Is there anything I could do to prevent that deletion and keep the HTML5 localStorage between different sessions?
Thanks!