Hans van der Meer via ntg-context schrieb am 19.11.2023 um 11:56:

I should have a first page without pagenumber and pagenumbers on the subsequent ones.
However the MWE here introduces an unwanted blank page from the call to \setuppagenumbering[state=start].

And the \setuppagenumbering has to come after the \page, of course.

Should I program otherwise?

There is nothing you can do here for the moment, the empty page is caused
by a new piece of code in page-lay.mkxl (see below) to go to the next odd page
when you use the \setuppagenumbering command.

page-lay.mkxl (line 1436):

\appendtoks
    \ifnum\realpageno>\plusone
        \page[\v!odd]%
        \setuplayout
    \fi
\to \everysetuppagenumbering

Wolfgang