<html style="-webkit-writing-mode:vertical-lr">
<div style="-webkit-column-count:2; border:5px solid blue">
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>

This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>

This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>

<div style="-webkit-column-break-before: always">
This text should be in the second column.<br>
This text should be in the second column.<br>
This text should be in the second column.<br>
This text should be in the second column.<br>
</div>
</div>

<div style="margin-block-start:1em; -webkit-column-count:2; border:5px solid blue">

This text should be in the first column.<br>
This text should be in the first column.<br>
This text should be in the first column.<br>
This text should be in the first column.<br>

<div style="-webkit-column-break-before: always">
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>

This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>

This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
This is some text.<br>
</div>