<div id="multicol">
  <div id="outer">
    <div id="middle">
      <div id="inner">
        line 1<br>
        line 2<br>
        line 3<br>
        line 4<br>
        line 5<br>
        line 6<br>
      </div>
    </div>
  </div>
  <div id="second" style="break-before:avoid;">
    foo
  </div>
</div>

#multicol {
  columns: 2;
  column-fill: auto;
  line-height: 20px;
  height: 120px;
  orphans: 1;
  widows: 4;
}