No recommendation here, but I'll note that your wish differs from mine and from the VAST majority of even technically-competent humans.
I wish for an easily portable, reliable, easy-to-use, well-supported (in apps and functionality) phone, which I can afford to replace as it becomes slow and outdated. I'm a huge fan of open-source hardware and software, and both have been part of my jobs in the past, but I absolutely don't want the hassle of self-customization or Twitter-level-customer-support.
Kids these days are comfortable upgrading PCs for gaming etc. I see no reason why they can't upgrade an open source phone. No one needs customer support anymore, we just swap a part or change software if things don't work. There is always Reddit for support. Modern kids are not technophobic even if they have no interest in IT careers. Modifying a phone would be no different than accessorising a dress to them.
Ok, this violates LW norms and I feel a little bad for not just walking away. But wow - if you don't see the difference between assembling a PC and troubleshooting a very specialized device with non-standard OS and DIY software/firmware, we're just not going to reach agreement.
Note: I would enjoy seeing your report of what you love and don't love, and some tips about how you use and upgrade YOUR open-source phone. Personal anecdotes go a long way, much more than theoretical arguments.
If Elon Musk could take over an existing open phone project, which one would you recommend? Example https://www.pine64.org/pinephonepro/ . A full list is at https://en.wikipedia.org/wiki/List_of_open-source_mobile_phones
I wish for a user upgradeable phone that yu do not have to discard just because its battery is not keeping up, or screen costs too much to repair etc.