WebAssembly by Mozilla would allow to write websites with any other language: https://hacks.mozilla.org/2016/03/a-webassembly-milestone/
If you meant a browser which is configurable in Python, like elisp for Emacs, look at http://www.qutebrowser.org/
cheers !
Fedora is usually pretty good at updating Qt and backporting security patches - certainly better than e.g. Debian. Not sure what the plans for Fedora 31 are exactly. If you want a newer Qt version, you could install one from binaries or build it yourself (note that the binary install won't give you proprietary codec support).
I'm writing a vim-like browser using PyQt and Python: qutebrowser
Yes, I'm crazy. Even though it eats all my free time, it's been a lot of fun working on it for nearly 2 years now, and I think it's better than the alternatives ;)