Long story short: Syncevolution was removed from Debian Bullseye. And the contacts importer script depended on it.
So we have two ways of fixing that, make a local package of syncevolution or re-upload it to debian.
Work to re-upload to debian being done here by a purism developer; Jonas:
Thus benefiting all debian based mobile distros.
The Librem Goodies package is waiting on syncevolution to be published in byzantium. You can still get it in amber.
If if you want a quick hack, you can download a syncevolution deb from here:
https://source.puri.sm/librem5-apps/syncevolution/-/jobs/368233/artifacts/download
Install it.
And then install Librem 5 goodies application debs from here: