Q:

Ubuntu 18.04 LTS Server npm : Depends: node-gyp (>= 0.10.9) but it is not going to be installed

My environment is a little different.
I updated from 14.04 to 16.04 to 18.04.
My desktop PC 18.04 has npm installed.
$ npm -version
3.5.2

# nodejs -v
v8.10.0

# apt install npm 

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 npm : Depends: node-gyp (>= 0.10.9) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

A:

Ubuntu Server 18.04 Node.js and npm install
sudo apt remove --purge nodejs npm
sudo apt clean
sudo apt autoclean
sudo apt install -f
sudo apt autoremove

Find the latest version at https://github.com/nodesource/distributions#debinstall
Latest version 10.x now
sudo apt install curl
curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
sudo apt-get install -y nodejs
curl -sL https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
sudo apt-get update && sudo apt-get install yarn

npm -version
6.1.0
nodejs -v
v10.7.0

