First, most memory is erased at the end of a normal shutdown/reboot sequence. This is implemented by the Linux kernel’s freed memory poisoning feature, more specifically:
page_poison- passing “P” to
slub_debug- zeroing heap memory at free time (
init_on_free=1)
That part was implemented into security-misc during Kernel Hardening - security-misc thanks to @madaidan.
But other parts mentioned there are yet to be ported and packaged. Not a trivial copy/paste task because some parts are Tails / ISO specific.