Otherwise, as unpleasant as it can be, you have to make a deal with Broadcom/Qualcomm, or get some other vendors to license their ARM chipset to you.
The latter doesn't seem like the end of the world to me TBH. Of course I'd love an ideal world where open architectures like RISC V have taken over and are actually usable, but until we get there usability remains more important than purity - unless you're RMS of course - even if it involves a small "deal with the devil".
I believe that most of the geeks out there love open-source products not much because they work daily with kernels and drivers (if that's the case then the argument for a pure open hardware without hex bloats makes sense), but because of the flexibility that they offer. Because they can install anything that they want on them and aren't prone to abandonware/planned deprecation like many products powered by Google or Apple. But if you don't give them products that they can use as main daily drivers, you'll rarely get enough momentum outside of the small tinker-and-show-off circles.
My iPhone 6S is more than 5 years old, and is perfectly usable as a daily driver (and my SO's iPhone 6 is too - it's 6 years old, only runs iOS 12, but still gets security updates and is perfectly usable).
It's fine if on the freedom/performance/up-to-dateness tradeoff, you're not pine64's customer.
Many people are.
If you're making a point about 5-year-old hardware being still useful today, I think you need to reference typical 5-year-old hardware. The 6S was weird (albeit in a good way).
If you want to change this, you'd need to either start a semiconductor company, or engineer some sort of coup at one or more of the "most unpleasant to deal with" Silicon vendors (Broadcom, Qualcomm, etc.).