Really depends on the specifics of what you're looking to do, and how much effort you're willing to put in. If you're looking to keep things simple and have a rather generic tube site, then just going with Django will get the job done. If you're looking to invest your time in something more intricate, then....
Frontend - React or Vue. This will give you a smoother experience updating and managing data, and also make it more feasible to develop single page/interactive websites (like YouTube or Twitch). You'll want webpack and in turn Node.js to write in it, but that's only to compile React/Vue into JavaScript to be used on your site. It might piss you off learning it, but it's quite beneficial.
API (with REST or GraphQL support) - Both Python and PHP will ultimately work. Python is generally a turtle for speed though, and is arguably best suited for scientific stuff, so that's something to keep in mind. Choosing neither and going with a compiled language, such as Go, is also feasible, but it really depends to what extent you're looking to scale and grow.
Database - For databases, something like MySQL or possibly PostgreSQL. Both support relational and non-relational (JSON) operations, which will no doubt come in handy. It seems trendy to go with MongoDB nowadays, but its dominantly non-relational nature will lead to unneeded complexity. But again, it really depends on the specifics of what you're looking to do.
At some point in time, Elasticsearch and Kafka may be relevant if you're looking to do some heavy duty stuff.
A PornHub developer gave an interview where he discussed their stack makeup, among other things. You might find it informative. https://davidwalsh.name/pornhub-interview.