LG G6 (H870) LineageOS 14.1 - Encryption not working
It's currently not implemented, the patch needs reviewing or something. I spent several days trying to figure it out. If you're into it, you can merge it yourself and rebuild and it should work: https://review.lineageos.org/#/c/165296/ (although I think this patch is for file-based encryption, there is a separate one for full disk encryption).