I was able to install the latest version with TWRP 3.0.2. I followed the steps outlined in this post:
https://forum.xda-developers.com/showpost.php?p=82459153&postcount=213 (see the end of the post and carefully change the LOS image zip file as stated.) I edited the ZIP file directly within 7Zip. At first I expanded the archive and edited the file and then I compressed it again but this did not work. After I edited the file inside 7Zip it worked. I did not investigate what the problem was.
I have a SGP612 (WIFI version with 32 GB) and it works very well with LOS 15.1.
The image for the LTE version is indicated on the first post of this thread. I guess it will work.
Thx for your reply :highfive:
If I understand you, than TWRP 3.0.2 is able to install the LOS 15.1 with the small tweak about the script inside the LOS-Zip? Do I have to root my device to do this, or will it work with an unlocked bootloader?
I've downloaded the LOS image from the first post as suggested, thx for your tip. LOS 15.1 is based on Android 8, right? Hope its stable...
I will wait for an answer regarding to rooting, hope it just works without rooting.