Long back i heard about HMD providing unlocked bootloaders for few of their devices. Why is Jolla not keen on adapting Sailfish for Nokia hardware and concentrating only on Sony? I don’t contempt Sony though, it is still a good option. But what is the reason for not trying out an alternative option? Moreover, Nokia devices can entice more people then Sony devices could.
This has been discussed many times. Apart from HMD promising, afaik they did not provide anything. Also SFOS needs quite more than an open bootloader. There are legal issues, too. See the thread for xperia 10 II f.ex.: XPeria 10 II + SFOS