https://github.com/genodelabs/genode/blob/master/ports/run/noux_bash.run line 123 I changed "de" to "us".
Of course, this change affect only make run/noux_bash After that, ":" key was where I expected it to be on my keyboard. Don't search too much, the code up to now seems to know only "de" and not "de".
But I am/was still unable to type Ctrl-] in the help to select a topic. Might be that Ctrl is not where I expect it yet.