[openhabian] how do I switch to OH 3.1 with openhabian?

Setup, Configuration and Use Installation
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1

I have openhabian installed with OH 3.0.1.
How can I switch to 3.1 stream (for example get 3.1 milestone build)?
Thanks
Pawel

2

option 41

3

Thank you very much. I was looking at the menu for so long I could not see it. It works.