Random hardware suggestions, using mobile Linux support as a litmus test

• Pinephone (Pro): Main downside is that OG Pinephone has extremely anemic hardware, and the charging circuit is not controlled through hardware for some insane reason; hope the kernel devs of whatever OS you put on it knows how to not turn your phone into a bomb. Also Pine64 as a company has gotten flak for their support of Manjaro. Can't deny how good the price is though.
• Fairphone 4: Good hardware, but expensive. I don't own it, but it works good on postmarketOS according to the wiki.
• Librem 5: Overpriced compared to the earlier members on this list, but you can guarantee the phosh interface will work well considering it was developed by Purism as well.
• OnePlus 6 and 6T: I don't know much about these, but they're very popular with the mobile Linux crowd.

As for the pixel, there's work on it but it's still broken at the moment. As for the hardware being too old, I haven't used anything Android in a while, so I don't know how much performance degrades each release, but a mobile Linux distribution should run just as good today as it will 20 years from now, assuming you use the same interface.