How to install LTS version of NodeJS on Raspbian

I am trying to install latest LTS version of NodeJS on Raspbian.

However, whatever I try, I get version 10.21.0, instead of 12.18.3

pi@rbpi1:~ $ node -v
v10.21.0

Generally, I am following the instruction on https://computingforgeeks.com/how-to-install-nodejs-on-ubuntu-debian-linux-mint/ :

sudo apt update
sudo apt -y upgrade
curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
sudo apt -y install nodejs

Synaptic shows only 10.x version to install. How to add 12.x or 14.x there?

What is wrong?