It's pretty trivial to do since those filters already exist.
It will probably end with retailers having to do that at the time of sale, but still, it's perfectly possible.
It gets even worse for Utah, though. The bill demands that any device activated in Utah comply with the law — not merely sold in Utah. So manufacturers would need to turn on location tracking and make it impossible to disable, for all users in the world, just to detect the corner case that they happen to be in Utah, so that they can silently turn on a Utah-specific porn filter.
I doubt the bill will pass, but if it does, I doubt many manufacturers would comply.
And I'm pretty sure "Verizon bloatware" is not installed at point of sale. What would stop a random employee from installing keyloggers? This stuff is centrally managed.
They'd very likely be losing money by complying with such a law. They wouldn't be leaving money on the table, they'd be taking it off the table.
They'd probably comply. Most could strike a deal with an existing company to provide software for this. Hell, more than likely a company who makes such software is probably a campaign contributor to many of the supporters of this bill.
AFAIK, the law doesn't define how effective the filter must be. So any good-faith attempt is probably more than enough. Even if the software is just a skin of Chrome with a add-on installed that blocks a list of websites.
I won't lie though, I would find it hilarious if foxnews.com was put into this obscenity filter.
To get such a law struck down, phone sellers would have to prove to the court that setting up Utah-specific phones would be excessively difficult.
I don't think it would be struck down with the commerce clause, but it would be close.
When Utah shut them down, someone else would start a web store selling non-compliant phones to Utah residents.