So yeah, installing node is sort of a stupid round about adventure in “do I want to deal with the old packaged version, or Do I want to bother installing it manually and being on the hook for updating it?”
I propose a middle ground with twice the madness
first, install npm via apt
sudo apt install npm
THEN install n with npm globally
sudo npm install n -g
then upgrade node with n
sudo n install latest
now update npm with npm
sudo npm install -g npm
profit?