boot – No Install Option on MacOS

I tried to install Ubuntu on my MacBook Pro 2018 following this tutorial.

However if I boot from the USB-Stick I do not get an option to install Ubuntu or to try it out without installing. I get the same boot menu like the guy in this question (first picture).

I have seen some other people with the same problem but no one had a solution for MacOS.

Does anybody know how to fix this issue?
Thanks.