So for the very kind of people who tend to not use Chrome because they're privacy aware and actually tend to use Ad-Blockers, and who are very likely to be fine with standalone apps, they don't make a standalone firmware updater app and instead make a Chrome only firmware updater.
I mean, I get it that in Linux accessing a USB-serial device from userspace can require an extra step (add user to "dialout" group), but it's hardly something that takes more than 1 paragraph to fully explain and you can do the check for access denied in the app and only prompt the user to do it if that error occurs.