From the other thread,

> Honestly been thinking about getting a alt OS myself for awhile.

Following directions for my phone, I went to:
https://github.com/phhusson/treble_experimentations/releases
and downloaded the -floss- .xz file.

You can learn more about 'alt osses' for you phone at https://community.e.foundation/ 
(yes, that really is a valid TLD. No I don't know how we went from .com & .org to .foundation; or when or especially why).

 Have a tactical turtleneck with scrunchie-face.