I really wish I could use Typst, but to be honest, it doesn't work with any journal I know of, let alone arXiv. It feels like a chicken-and-egg problem to me; I can't see most people who use LaTeX moving over unless journals and preprint servers adopt it, and I can't see journals or preprint servers adopting it unless people move over. Still, it's early days, I and wish the community good luck and I genuinely hope that one day I can ditch LaTeX for something markdown-like.