Installing rom zip through TWRP replaces recovery instead of intalling os I formatted my Oneplus 6t and was able to install TWRP, but when I install the zip for LineageOS, instead of installing it as the OS, it just replaces the TWRP recovery with a Lineage one, and I am still unable to boot into system. 
Log.txt
alright I actually figured it out: the trick is to flash the stock ROM using this tool and then fastboot TWRP, install the TWRP and then install Lineage all without formatting the internal storage. I don't know why that works, but it does.