Custom-RenderPipelineCore VS MarrowSDK

I have been trying for 1 hour to add the three packages necessary to upload a custom avatar and every time it says [Package Manager Window] Cannot perform upm operation: Unable to add package [https://github.com/StressLevelZero/Custom-RenderPipelineCore]:

You need to be able to 3d model if you want to make an avatar from scratch, then look here for more info https://github.com/StressLevelZero/MarrowSDK/wiki/Avatars

/First install git then do https://www.youtube.com/watch?v=3tzfabwVdu0 /then https://www.youtube.com/watch?v=YhVFO7HTcWA . /official guide thats not that good https://github.com/StressLevelZero/MarrowSDK/wiki / this ones bit advanced but good if you already have everything set up and understand unity https://docs.google.com/document/d/1M4n8rPY86q2gRuu5K9yPEZC9Cr6t6cJF5plLhFU3dqs/edit. There's more but I don't think its neccesary. Also this might be hard if you have no experience. Especially because the sdk isnt full out and the game hasnt been out for that long so not many tutorials. good luck :)

You don't really need to model anything - you just need to take Simon's model - which is probably already rigged for you, then follow along with the Marrow SDK documentation on how to make an avatar. There's even a video guide series here too. If you think you'll need a 3D modelling program, I'd recommend Blender. It's free, and I've been able to run it on stupidly old laptops from the early 2000s before without too much of a hassle (obviously it'll run better on more modern systems, but you work with what you got).