Hi Matthieu,
GCC 15 is, to me, a bad idea this cycle. A majority of the applications in Debian Multimedia, when @doko did a test rebuild there, failed to build from source. I received over 100 emails in the debian-multimedia mailing list.
If this goes through, it is sure to kill Ubuntu Studio. I, for one, don’t have the time or bandwidth to go through and patch over 100 packages in less than two months.