Package: linux-image-powerpc64le Version: 4.15+91 (I know its not the right package as this is an issue only in the testing CD, not a running system, but I can't seem to find the right package to file against, and figure this will at least CC the right people, sorry about that).
Pretty self-explanatory, algif_skcipher mod is missing on the weekly buster install CD/DVD, so any time you try to use encrypted volumes you get a cryptic error in the install prompt and a "Error allocating crypto tfm" error in dmesg.
