Bootstrap 4 - I don't want columns to have the same height

Yes, you can use d-block on the row, and float-left on the columns to make it work the Bootstrap 3.x way with floated columns instead of flexbox..

<div class="row d-block">
    <div class="col-lg-3 float-left">
        ..
    </div>
    <div class="col-lg-9 float-left">
        ..
    </div>
</div>

https://codeply.com/go/Ghhq1NbMDG

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Bootstrap 4 Columns float style like Bootstrap 3 is it possible?
Empty vertical space between columns in Bootstrap 4