Excellent question. In fact, uBlas in mainly C++98 with a bit of C++11. It's an old code base which need to be refreshed. So as you correclty guessed, I want to bring in uBlas more modern C++ technology, up to C++20 and where they make sense.
Backward compatibility is important but I think we need to improve this library anyway and C++98 is a bit ... huh... outdated now.
During the project, the student will have to prove that each feature brings a real benefit, generally in term of speed as far as uBlas is concerned, or in term of ease of implementation for example.
But if having "ranges" of "spaceships concepts" multiply the speed by 10, then yes C++20 will be required. OK Just kidding :-D