Thanks for the info about the versioning logic.
What I'm trying to achieve is simply to be able to unlock my root partition (Cf explanation in my first post), what I could not do anymore after upgrading to 6.1.115. I do not remember choosing a rolling release distro, used for almost a year until this kernel update broke everything.
My update to trixie was simply motivated by the hypothesis that, because of the kernel update, some incompatibility with cryptsetup (resp. dropbear, initramfs.....) might have occurred and could explain this abrupt behavior change. Obviously, it did not but keep in mind that the problem is anterior to any of the changes I realized in the userspace. In a nutshell, my initial problem remains and I still do not get why. Again:
the kernel seems compiled with the proper option
initramfs points to the proper libraries.
Is dm_mod kernel module loaded?
cannot use device rootfs name invalid or still in use
IYO, is it really a matter of kernel module availability? cryptsetup-initramfs and dropbear-initramfs are available, to my knowledge, UUID are stable entities
cat etc/crypttab
rootfs UUID=7afe59bd-ca3d-4618-ae75-f2e9b417eb71 none initramfs,luks
So I just don't get it.
I also just try 6.12 but rollback because my system did not even boot despite of the proper symlinks in the boot partition