Here’s an example of a very simple scene with SuperTextMesh, TextMeshPro and Legacy Text

The bottom three are identical, the top one has an extra ContentSizeFitter as the docs suggest, which does kinda help, but still causes the layout to be wrong.

The exact setup is created following this short video https://www.youtube.com/watch?v=W4tUQr9Tv3g, in short it’s simply a text item with two nested VerticalLayoutGroups set to Control Child Size.

Could I see a screenshot of the inspector for the STM components? Basically, there's a couple settings in STM that are there for legacy purposes, so it's possible for STM to follow a layout wrong or differently if not configured right.

For the contentsizefitters, make sure they're set to "preferred size"... even though the verticallayoutgroup has a notice that pops up, iirc, it seems to be the right way to do this kind of thing if I'm understanding correctly...?