I will answer my own question in case someone is trying to find an answer:
How can you disable apk signature verification for android 5.1.1? (I came here from Vanced.app)
I have Magisk on my device.
1. Installed Xposed Framework under Magisk (the one that works for Android 5.0 to Android 8.1)
2. Installed XposedInstaller(3.1.5) from the instructions in Xposed Framework description inside Magisk Manager
3. Installed Xinstaller by pyler. (another alternative might be InstallerOpt (last updated January 2017) a fork of abandoned Xinstaller)
4. In Xinstaller chekmark Expert mode. Then on Misc checkmark Disable Verifying signature (reenable this as soon as possible)
Of course this is if you don't want to use a warez app that is not allowed to be mentioned in these forums.
https://repo.xposed.info/module/com.pyler.xinstaller
https://repo.xposed.info/module/net.fypm.installeropt
I tried to search but couldn't find answer. Sorry if it has been mentioned.
Trying to install vanced but my version of Android is 5.1.1 so can not use Smali patcher as they mention on their website.
Also the Magisk module for vanced has been abandoned.
So anybody running into same issue has found a way to disable apk verification?
My device is running LineageOS 12.1. It has root with Magisk.
Oh! Forgot to mention I was able to install an older version but when I started the app it demanded I installed Google services which I am trying to avoid in this tablet. It occurred to me that maybe vanced can't run without MiniG in anycase.. although I think it is supposed to be able to work without it on rooted devices.
Thanks.