stack recommendations for a lateral mover (2022)?

Working as a "quant" right now but I want to broaden my horizon into web development (have some ideas that I want to try to build, and also want to futureproof a bit because I moved to a location with few opportunities for quants). I have a math background and I do lots of programming - Matlab, R, Python, even some web apps in R/Shiny and hosting my own, very basic static site - but it's nothing like modern web development as far as I can tell (the crux is usually the math/stats modelling and data handling). It's just dizzying trying to get on top of how many web dev tools/frameworks/languages there are and how fast everything seems to be changing.

Been lurking here and reading up for a while, I just wanted to ask for some tips before I start. I feel like I have a decent grasp of the programming basics (data structures, OOP,...) and Linux CL, and I have an idea for a simple (Sudoku) app that I'd like to build. My idea was to look for tutorials and try to build that app using eg Next.js/React, Tailwind and TypeScript (hoping that those are among the most recent and will be state of the art at least for a while), and then try to host it using something like Heroku or Netlify. I found [0] quite inspiring and plan to use the stack as a bit of a reference. I don't think I'll need a backend yet, but later I might like to add some functional language (eg Erlang or Clojure) to my stack because I like the paradigm intellectually, if that makes any sense (over something like Go or just using Python which I already know). I know how to write SQL queries (and also data modelling/normalization), I don't fully understand what difference eg Postgres vs SQLite would make once I need a DB (other than that the latter is easier but has a hard limit, apparently). Any thoughts on that plan, tips/suggestions/things that I'm missing?

[0] https://news.ycombinator.com/item?id=32376154