Earlier quoted context omitted.
That's precisely the thing we should avoid. Learning on free software like LibreOffice Calc would be better just like learning GIMP would be better than students learning Adobe Photoshop and demanding employers buy these licenses/subscriptions. You can self-host Git, but there's also plenty of alternatives that are built as free software.
You are fooling yourself if you think libreoffice has feature parity with ms office, and gimp with Photoshop. Gimp doesn't even have feature parity with krita.
How many advanced GitHub features not present on other platforms do you think students are using? If the answer is none, then there's no reason to choose a proprietary service they can't hack on and are required create accounts with a for-profit entity.