Interesting, thank you for sharing. Nothing new since 2017 if I understand correctly? I understand that the C++ proposal system is very slow, still it would be nice to know if that’s still something people are working on. I would personally love to see something like this in the standard!
A lot of work has been done since 2017: the proposal is at its 9th revision (http://fmtlib.net/D0645R9.html) and is prioritized (but not accepted yet) for C++20.