Mozilla had the right idea with FirefoxOS - doing everything as HTML. All the apps people give a shit about are glorified browser windows anyway. What Mozilla fucked up was aiming for a low-end market... with an OS defined by constant power / performance overhead.

Every application in any modern phone could be transpiled HTML5 and you would not know the difference. If it's not "one o' them Genshin Impacts" then it probably already is.

But they already have a "Nothing OS": https://en.wikipedia.org/wiki/Nothing_Phone_1#Software

And they are calling that an "OS":

“If you think about the tech stack for what an OS is, I don’t think we need to work on the lower parts of the stack — drivers and how hardware connects to software and the kernel,” Pei added. “I don’t think we need to work on that, but we should work on innovating the user experience, because operating systems haven’t really changed for 40 years.

Yeah, they speaking about another freaking skin...

He's already done shady shit, like build his company as a remote work startup during the pandemic, then pulled the rug out from under his employees by mandating full time in office, adding that people who try to work from home are childish.

Addendum:

If you think about the tech stack for what an OS is, I don’t think we need to work on the lower parts of the stack [...] but we should work on innovating the user experience, because operating systems haven’t really changed for 40 years. [...] these devices have so much information on us [...] but they don’t leverage any of that information to make the experience any better.

Now this, I wholeheartedly agree.
I feel there's a looooot of room to try new, innovative, potentially even wacky user UIs and experiences, Sailfish OS and Nintype/Minuum being my favorite examples of a existing concept being done with completely fresh UX, HOWEVER

Not having to work on the lower part of the stack??? What???

If we're talking about x86, sure I guess, throw a Linux kernel on it and build whatever on top but ARM, specially on phones, looks like a compete hellscape! (to a outsider like me)
Ask any Linux phone Dev how easy it was to get the hardware going. Their heads will likely start spinning.

Could you build a new, modern mobile entirely from components with Mainline Linux support? And did this support come from the manufacturer or was it hundreds of hours of painful reverse engineering from the community?
New phone without having to work on the lower parts of the stack??? Dunno bout that man.

why bother with the new OS?

So someone's petty little sanctions don't obliterate your business. It's worth having a backup.

They already have it. It's called... surpise-surprise.... Nothing OS.

from their website:

Nothing OS 3.0

Powered by Android 15. Open Beta is out now for Phone (2a).

These companies might want their platforms to be free from google's control, but that's only because they want to have that control for themselves.