Are iPhones subject to ransomware attacks?

A neighbor asked me for help with an iMac that had fallen victim to
a ransmomware attack ("this computer has been locked, call the number
below....").

I'm left wondering if iPhones are subject to similar attacks, since
they offer most of the services found on desktop computers including
browsers. The subject computer was reasonably up-to-date and only a
couple years old. The hijack was during an attempt to connect to
MapQuest using the Safari browser. The screen seemed locked and I
didn't know how to recover control. Is there a force-restart- to-
safe-mode for iOS or MacOS?

Are iPhones subject to similar attacks? If not, why?

Thanks for reading, and apologies if this is a dumb question!

bob prohaska