The offline version works via Electron, and from looking around (e.g. https://www.github.com/electron/electron/issues/12712) it seems that the only way to make that work is to have ChromeOS users enable "developer mode".
Probably the easiest well-integrated option here is to look at the "progressive web app" situation for UltraBox and fix up issues if any exist there. I think that, without some extra work, a PWA wouldn't have "local custom samples", though.
The offline version works via Electron, and from looking around (e.g. https://www.github.com/electron/electron/issues/12712) it seems that the only way to make that work is to have ChromeOS users enable "developer mode".
Probably the easiest well-integrated option here is to look at the "progressive web app" situation for UltraBox and fix up issues if any exist there. I think that, without some extra work, a PWA wouldn't have "local custom samples", though.