I'm not a developer, I only know some basics but for what I've seen and have learned on Hive something very useful besides HTML would be CSS and JavaScript. That would be for frontend development, for the backend developers also use a lot of JavaScript with other technologies.
Las year I started learning how to code and found this website: https://www.freecodecamp.org/ (it's free). My journey took me somewhere else but it might be useful for you. I still want to learn how to code but right now I'm too busy working in other areas so maybe I'll just partner with a coder, I already have a friend who knows a lot about this, and he is learning how to code on HIVE.
I was not asking for me. I would not want to rekindle my HTML experience 😇 I was asking this for others who may want to get into this theme. Thanks for the info.