Why are all my imported Unity assets / models pink?
I ran into this problem when I was trying to import a known-working asset pack into a new Unity project. Long story short, it was all because I chose one of the new rendering pipelines without understanding what I was doing. Yes, noob error.
It has something to do with URP, materials and shaders. Way beyond the author's technical understanding at this moment. I'll come back later when I know more and explain it.
To fix it, within your project, click Edit > Render Pipeline > Universal Render Pipeline:
Choose either the whole project, or select one material in the hierarchy and upgrade just it. both ways worked for me
I hope this helps! Unity 2019.3.7f1 (Unity 2019.3) "Universal Project Template"