They exist but they need more polish and support from device vendors to be a viable alternative to the duopoly. It should be just as easy for the average phone buyer to get and use a 'Linux phone' as it is to get an Android or fruit phone. This is more or less true now for Linux distributions no matter what the naysayers keep on repeating, the next step is to make it true for mobile devices. There will still be naysayers but... who cares? Let them listen to themselves in their echo chambers like they've been doing w.r.t. 'Linux on the desktop'.