Would also love to see some starter project with shopping cart functions.

Here are some options:

• contact https://forum.mendix.com/link/space/studio%20pro/questions/115737, ask for a copy/fork.
• https://www.mendix.com/solutions/omnichannel-integration-layer/ “Brick-and-Mortar e-Commerce“, but no code or project there, just a picture.
• ask Mendix to fork their shop: https://mendixshop.mendixcloud.com/index3.html.
• ask Robin Bozhurin about https://github.com/rbozhurin/Mendix (which is empty, but he at least intended to build a shop in Mendix)
• see what Andy made in 2017: https://github.com/andylushman/E-Commerce-Store

Searched github.com/mendix, nothing.

And my comment here: https://forum.mendix.com/link/space/other/questions/109337 a year ago.