I have laid Lineageos in this way, so I guess it might be coming out?
Method 1: Updater Script Hack to fix Error 7
Note: Use this method only when you’re 100% sure that the ROM you’ve downloaded is for your device. What this does is to bypass assert checks in recovery so that you can install the ROM without any checks.
Open the Lineage OS ROM zip using any archiving software like 7zip, WinRAR, etc… You can also open it on your device.
Now, you need to navigate to this path: META-INF » com » google » android » updater-script.
Open the file updater-script in a text editor. You’ll see a bunch of lines with the command assert and the model name of the device next to it.
If there’s a mismatch with the codename of the device in the script, you’ll get Error 7 while flashing.
So, just either edit the code to match your device’s codename or delete all the lines having the code “assert & getprop”
Save the file.
Try to install the ROM now.