Hello,
Yeah, the outline shaders currently aren't supported in-editor for URP/HDRP. I've heard reports of them rendering fine in built games, but that'd still make development hard. I wrote this script that emulates the outline effect and works in URP: https://pastebin.com/wWv49mgG So try placing this on the STM object you want to have an outline.
A new outline shader that looks better than the current one and works in URP is (still!) in the works by a third party. I ask for a bit more patience on the completion of that.
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Text lining up with the bounding box is what the "baseOffset" feature is meant for! So you can tweak that offset per-mesh to centre text. I'd do it automatically, but the bounding box is already created based on font bounds, so there's no real way for me to figure out how to nicely space stuff, so I think the baseOffset feature is a good solution.
Regarding this, I actually wrote a script for applying settings like this to multiple STM objects at the same time, called "STMPresets". So... you just have to change the data on one scriptableObject, and all STM objects referencing that SO will update automatically to match the new settings. So you can say... "Font: arial BaseOffset: x=0, y=0.4", and that will just be applied to all meshes listening to that preset. It's been working well in a personal project of mine, so I might include it as a utility script in the next version of STM? If you think this would help with having to manually adjust text, I could upload an early version to pastebin for you!