I downloaded debootstrap's source from:
https://git.devuan.org/packages-base/debootstrap and built a .deb
package on Debian Testing. Then, I used the freshly installed
debootstrap to install Devuan as follows:

# debootstrap --arch amd64 jessie /mnt/sda8 http://packages.devuan.org/devuan
W: Cannot check Release signature; keyring file not available
/usr/share/keyrings/devuan-keyring.gpg
I: Retrieving Release
I: Validating Packages
I: Resolving dependencies of required packages...
I: Resolving dependencies of base packages...
I: Checking component main on http://packages.devuan.org/devuan...
E: Couldn't find these debs: sysvinit-core

Any hints as to what I should do, are most welcome.

Thanks.