RuntimeException (400)

Hello! I downloaded GetGrav with the admin plugin, extracted it on my web server, set up an admin account and downloaded your theme getgrav-grav-theme-learn2-1.6.0-0-ga615cf5.zip and did what the instructions showed:
1. Created a folder learn2 in /user/themes
2. Extracted the files into learn2
3. Changed the active theme to learn2
4. Disabled caching in the Admin settings panel

Then I opened my website. I can see the new design, but also a lot of error messages:

RuntimeException (400)
Template "default.html.twig" is not defined.


Sounds like some important steps are missing from https://github.com/getgrav/grav-theme-learn2/#manual-installation?

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Can be deleted. Was automatically fixed after using a different browser :(