If anyone wants to give it a shot again, don't start with a GNU/Linux phone, start with something the masses actually will care about. Reverse-engineered, adversarially-interoperable social media apps for all the mainstream networks with no ads/dark patterns? Cool. Adblocking by default? Sure thing. Built-in support for a wide range of cloud providers (including standard protocols such as SFTP/S3/etc). And so on.
Address actual pain points that people have. "GNU/Linux" by itself does not address anything. The non-technical majority don't even know what that is or means, and even for technical people it isn't a perk by itself - sure, you can run whatever software you want... but you (or someone else) still need to write said software to begin with... or you could just trade a bit of money and "freedom" and buy an iPhone which doesn't have any of those problems.