Does the OnePlus process work for people? They've got a form that allows you to beg them to let you unlock your phone, but it's never worked for me. Motorola works similarly but it does work, which is why I stick with them.
If the process requires anything beyond "internet access" I'm not purchasing the device.
I did have to be careful to buy the variant supported by lineageos. (I think the t mobile version of this phone does require using op form, which I've heard rarely works.)