mupdf 1.20.0 is coming to rawhide in side-tag f37-build-side-54574. As always, I coordinate this with the maintainers of zathura-pdf-mupdf and python-PyMuPDF directly via PRs (but I may have missed some indirect dependency).
... so fi you click on "send" a second time (in hyperkitty) because the 1st time appeared to have no effect (no reaction, no browser indication, just the form sitting there) you can send the message twice. Oh well. Patience ;-)