https://docs.magicmirror.builders/getting-started/installation.html#manual-installation

Paragraph 1.
“Download and install the latest Node.js version, see the official documentation:”

No that’s wrong. It is very difficult / not possible to follow those instructions if you have a Raspberry Pi. Beginners will have to debug for hours to get this working.

Just two commands are enough:
sudo apt-get install npm
sudo apt-get install nodejs -y