The command \setupMMLappearance[mtable][alternative=b] used to give me, in
mkii, MathML layouts in which the first column was ragged left, the second
column centred, and the third column ragged right. It now seems to be
ignored, and the output has all three columns centred.

Minimal working example showing the problem:

\usemodule[mathml]

\setupMMLappearance[mtable][alternative=c]

\starttext

Some text.

\xmlprocessdata{}{<formula>
        <math xmlns='http://www.w3.org/1998/Math/MathML'>
         <mtable>
          <mtr>
           <mtd>
            <mi>x</mi>
            <mo>+</mo>
            <mi>y</mi>
           </mtd>
           <mtd>
            <mo>=</mo>
           </mtd>
           <mtd>
            <mn>2.56</mn>
            <mtext> million</mtext>
           </mtd>
          </mtr>
          <mtr>
           <mtd>
            <mi>x</mi>
           </mtd>
           <mtd>
            <mo>=</mo>
           </mtd>
           <mtd>
            <mn>2.56</mn>
           </mtd>
          </mtr>
         </mtable>
        </math>
      </formula>}{}

Some more text.

\stoptext

What is the successor to \setupMMLappearance please?

Thanks very much.

Duncan