Text mesh pro - Vertical Text

change gui width to zero and give some positive height.

There is a rotate tag which rotates each of your letters. So if you rotate them by 90 degrees, then un-rotate your gameobject by -90 degrees, you'll have a text object which you can rescale to your hearts desire, and which even works with paragraphs (docs.unity3d.com/Packages/com.unity.textmeshpro@4.0/manual/RichTextRotate.html)

You will probably need to increase the spacing per character in the spacing options, as there may be some intersecting letters now that the characters are rotated, but as long as the WD% in the auto size options is low enough (or ideally zero), it should work without a problem. If you want to go the extra step you can even create a custom stylesheet option in "Assets/TextMesh Pro/Resources/Style Sheets/Default Style Sheet.asset" which will automatically add the rotate tag (and maybe a vertical offset tag) at the beginning and end, and that way all you have to do is change the text sytle dropdown from normal to your new style sheet. (gameobject rotation and character spacing will have to be done manually though)

docs.unity3d.com/Packages/com.unity.textmeshpro@4.0/manual/StyleSheets.html

@Larry-Dietz This should also work with auto-sizing, as opposed to just setting width to zero

keep wrapping enabled and set width size to something that can contain the character without size reduction, it'll work with auto-size too.