@bhepler Thank you for your clear and precise instruction, I have now got it working, it did show me an error at the end of the installation but it still seems to work:
npm WARN grunt-stylelint@0.8.0 requires a peer of stylelint@^7.8.0 but none was installed.
npm WARN stylelint-config-standard@16.0.0 requires a peer of stylelint@^7.8.0 but none was installed.
Dependencies installation Done!
Check plymouth installation ...
Splashscreen: Checking themes directory.
Splashscreen: Create theme directory if not exists.
Splashscreen: Theme copied successfully.
Splashscreen: Changed theme to MagicMirror successfully.
bash: line 153: syntax error near unexpected token `then'
bash: line 153: `then'
again thank you for taking the time from your day to help, much appreciated.