seeing as I don’t see any way to do it outside of runtime
If the expressions are static, you could output to a png with https://www.latex2png.com/ or convert the pdf to png (for example, with ImageMagick: graphics - Compile a LaTeX document into a PNG image that's as short as possible - TeX - LaTeX Stack Exchange).
If the expressions need to be changed during runtime, it’s do-able for example GodotTeX. So I suppose you could mimic it with the brand-new C# Native Extension support Defold + C# support.