Yeah, ChromeOS is a linux distro that boots chrome and is now being officially split into Lacros (Linux and ChromeOS), but honestly, we should be able to make a “distro” that just starts a DE with firefox or chromium as the main window. Extensions could be written that present the filesystem in firefox or chromium and most users would be none the wiser.
Call it WebOS or something.
Does something like that already exist?
Unless you really need/want browser only, you might get away with any “lightweight” distro depending on the specs of the machine.
I assume you’re trying to install on something like a Chromebook. This might get you in the right direction. https://www.linuxfordevices.com/tutorials/linux/best-linux-distros-for-chromebook
It would have a lot more functionality too.