• nodejs 12.19.0
• npm version 6.4.1
• Windows10
• 64bit:

What steps will reproduce the bug?

installing latest version of nodejs 12.19.0 when having npm version 6.4.1 in %APPDATA% will get you in a situation where you can not update npm anymore.
npm install npm@latest will report that npm version 6.4.1 is not supported by the current version of nodejs.
although nodejs installs a more recent version of npm in c:\program files\nodejs, it will still use the version from %APPDATA%

• tried to remove %appdata%/npm from PATH, but even then npm was run from %APPDATA%
• the only solution was to examine what command was run when executing npm.cmd (apparently node.exe node-cli.js) and explicitity running command with full paths:
  "c:\Program Files\nodejs\node.exe" "c:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js" install npm@latest

What is the expected behavior?

I would expect to be able to update npm at any time , perhaps by providing an option to run npm from nodejs folder...

What do you see instead?

npm 6.4.1 is incompatible with nodejs 12.19.0