It sounds like you’re now running an unsupported hybrid of Kicksecure 17 packages on top of Debian Trixie. Kicksecure 17 packages were only supported on Debian Bookworm, and are currently unsupported on all except for Qubes OS. See:
The recommended way to upgrade a Kicksecure 17 system to Kicksecure 18 is to use the /usr/sbin/release-upgrade script, which has several workarounds in it to make sure the upgrade is more likely to go smoothly. Now that you’ve upgraded the base system to Trixie though, it’s potentially too late to use it successfully. Upgrading your Kicksecure packages to Kicksecure 18 will most likely not work either, since the fixes the release-upgrade script would have applied won’t be applied.
At this point, your best bet is probably to reinstall the system from scratch, either using a Kicksecure 18 image, or using a Debian Trixie image and then distribution-morphing it into Kicksecure 18.