Fairphone and Librem are alternatives to Pine64 hardware in the same way that a Lamborghini may be an alternative to a Toyota Yaris. They aren't even remotely in the same pricing band.
They are still alternatives… with different pros and cons, the price being one of them.
But the Fairphone is not an alternative to the Librem 5 and the PinePhone, and those are not alternatives to the Fairphone. They target different things.
It's not necessarily open source hardware, but there's the option of getting a used or new old stock phone that works with a distro like postmarketOS, or /e/ phone, etc.
The Gigaset phones might be interesting. Built in Germany, rebranded by Volla among others.
Sony Xperia and Fairphone are far away from vanilla Linux I think (someone may correct me).