Please look into porting SFOS4 to the good old OnePlus One (bacon).
The phone is working brilliantly under SFOS 3.4. However, the current porter, @wdehoog, mentioned he was unable to continue working on this project in part because the current image is built on kernel 3.4.67 (based on CM12.1) whereas SFOS4 would require a more recent kernel version (citation: Sailfish OS for OnePlus One | Page 138 - OnePlus Community).
Nevertheless, as boosterjuan pointed out on that same OnePlus forum, there actually is a newer kernel for bacon available here: GitHub - erorcun/android_kernel_oneplus_msm8974-3.10: 3.10 kernel for Bacon running CM. Also perhaps a more recent version of LineageOS (lineageosroms [dot] com [slash] bacon) might be helpful?
On a personal note, I would hate to see the OnePlus One becoming obsolete. It is still great hardware and @wdehoog’s adaptation left nothing to be desired. On top of that, it seems like this device is still pretty popular. Thus, quite a bunch of people might be really happy about a future perspective for their good old OnePlus One.
So, please please please port SFOS4 to bacon!!!
P.S. I could not add links at liberty. Therefore, I had to improvise. Sorry about that.