Rooting again after installing LineageOS? After following the following steps:


rooting a motorola g3, 
installing TWRP 
wiping the phone (without micro-sd present) with TWRP
installing lineageOS
wiping the phone (without micro-sd present) with TWRP
Installing SlimOS
wiping the phone (without micro-sd present) with TWRP
Installing LineageOS
Installing Root checker basic
Finding it does not have proper root acces
Rebooting to fastboot>recovery>TWRP>Install 
Installing http://forum.xda-developers.com/attachment.php?attachmentid=3655401&amp;d=1456122222 (as linked specifically for the Moto G 3 2015 generation here: https://motog5.net/unlock-bootloader-install-twrp-root-moto-g3/)*
Rebooting, 
checking Root checker basic
Finding it does not have proper root access
Noticing this explanation: https://duckduckgo.com/?q=root+lineage&amp;atb=v119-6&amp;iax=videos&amp;ia=videos&amp;iai=L8rwPV5ZhhA
enabling in debugging mode:
Root access for ADB and All apps
checking Root checker basic
Finding it does not have proper root access
Reboot in fastmode>TWRP>Install the supersu file
Reboot check in Root check basic whether root has been obtained, root has not been obtained.
Root access for ADB and All apps
checking Root checker basic
Finding it does not have proper root access
Reboot in fastmode>TWRP>Install the supersu file
It does not give a red error bar but it reads:



  Boot image patcher
  
  
  
  
  Finding boot image
  --- Boot image:/ /dev/block/mmcblk0p31
  Extracting ramdisk
  Decrompressing ramdisk
  Checking Patch status
  Creating Backup
  Patching sepolicy
  --- Failure, aborting
  
  
  
  
  Important notice
  
  
  
  If TWRP offers to install SuperSU do NOT Let it!
  
  


I thought perhaps the supersu file needs to be changed since now it is for a LineageOS in stead of for the MOTO G3 2015 edition stock android, so I tried the following 3 files as well:

From:
https://www.lineageosrom.com/2016/12/how-to-enable-root-in-lineage-os-using.html
TO:
https://www.lineageosrom.com/2017/01/download-supersuzp-and-su-removalzip.html
To:
https://download.lineageos.org/extras


https://mirrorbits.lineageos.org/su/addonsu-15.1-arm-signed.zip
https://mirrorbits.lineageos.org/su/addonsu-15.1-arm64-signed.zip
https://mirrorbits.lineageos.org/su/addonsu-15.1-x86-signed.zip


Only the 3d did not give a red error.

So as much of a trivial challenge it may appear to be, I was curious if anyone can point out which mistake I am making in trying to give the device root-access again. Other suggestions are welcome as well!

*Note, this was also the file that allowed me to root it the first time.
As you've already found out, LineageOS has its own, built-in, lightweight SU solution (addonsu), which is the only one supported officially (the team does not adore Magisk/SuperSU).

Note that officially LOS only provides 14.1 builds for your device. Assuming that's the version you're running, using the addonsu for 15.1 you will naturally bump into problems. As indicated in the source, your device is an arm one, so use addonsu-14.1-arm-signed.zip instead.

Magisk/SuperSU are reported by other users to work well enough, but you will need newer packages that work with higher Android versions, and the one you initially used (SuperSU 2.62) isn't enough.