>>11418157I made a 4chan clone.
So there are a lot of different ways it can be done.
The front end needs to be in html/css/javascript one way or another. Thats simply the only way to render things. I used this wonderful front end programming language called Elm to do all the front end stuff.
Message boards are simple and straight forward enough that if you really wanted, you dont need to code much for it at all on the backend. Services like firebase exist that can just be your back end database with little to no programming (that is what I did).
Or, I could imagine you could do it completely differently than how I did it, and be very backend focused, and make a database, and a webserver that just sends html and css it generates on its own, and then not write any JavaScript.
For the backend, almost any language will do. Every language has some kind of web server framework.