This is this bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1067398
You need both of python3-numpy 1:1.26.4+ds-6 mrbuild 1.9 This failing build you have has the former but not the latter (you have mrbuild 1.8). What is being built? Is this Ubuntu's version of experimental? I believe both of these packages are in Debian/unstable right now, hence it builds fine there (yes, unstable has python 3.11, but the error you're seeing is exactly what mrbuild 1.9 fixes). mrcal 2.4.1 made it to Ubuntu/noble, right?
