There is no doubt on the issue of chicken-and-egg problem with the app ecosystem, but wouldn't it be the only problem or even say the major problem to address if the manufacturers get on to supporting mainline Linux for smartphones instead of developing a completely new operating system from the scratch.
That leads to the same problem that killed Netbooks, besides the XP price dumping, and also plagues the PC and Android eco-systems, differentiation.
Mainline GNU/Linux isn't something that makes average consumer pick vendor A or B when looking for a new device at the shopping mall.
And the hardware alone also doesn't sell, it must be the whole vertical experience on how software + hardware work together to bring that experience into existence.
I think the differentiation issue would persist no matter what OS a smartphone manufacturer come up with at this point if it is open-source, which it should be in order to get more manufacturers on board for getting apps developed for it and thereby risking fragmentation.
> And the hardware alone also doesn't sell, it must be the whole vertical experience on how software + hardware work together to bring that experience into existence.
This is exactly why Librem 5 is more promising as Purism develop both hardware and software.