Forum post with downloads of maybe a more receint version now maintained unofficially.
https://forum.xda-developers.com/galaxy-s3-t-mobile/development/rom-lineage-14-1-unoficial-d2tmo-4-10-18-t3776477
The official Wiki for LineageOS with instructions.
https://wiki.lineageos.org/devices/d2tmo
More instructions for installation with broken download link.
https://www.lineageosroms.com/2017/01/lineageos-rom-samsung-galaxy-s3-tmobile.html
More instructions and broken links.
https://www.cyanogenmods.org/forums/topic/galaxy-s3-t-mobile-lineage-14-1-android-nougat-7-1-rom/