Oh, and I finally did manage to recover the output where I noticed the problem (from a script which runs debdelta-upgrade` followed by `aptitude upgrade`):
[...] Recreated debs are saved in the directory /var/cache/apt/archives Deltas: 1 present and 0 not, downloaded so far: time 0.23sec, size 10kB, speed 43kB/sec. Need to get 21kB of deltas. Downloaded, time 0.04sec, speed 311kB/sec, libzbar0_0.23.92-7_0.23.92-7+deb12u1_amd64.debdelta Patching done, time 0.14sec, speed 886k/sec (script 0.11sec 1153k/sec)(unaccounted 0.03sec) Created, time 0.14sec, speed 886kB/sec, libzbar0_0.23.92-7%2bdeb12u1_amd64.deb Delta-upgrade statistics: downloaded deltas, size 21kB time 0sec speed 79kB/sec patching to debs, size 126kB time 0sec speed 885kB/sec total resulting debs, size 126kB time 0sec virtual speed 132kB/sec Reading package lists... Done Building dependency tree... Done Reading state information... Done The following packages will be upgraded: libzbar0 1 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 130 kB of archives. After unpacking 0 B will be used. Do you want to continue? [Y/n/?] Get: 1 http://security.debian.org stable-security/main amd64 libzbar0 amd64 0.23.92-7+deb12u1 [130 kB] Fetched 130 kB in 0s (880 kB/s) Retrieving bug reports... Done Parsing Found/Fixed information... Done Reading changelogs... Done (Reading database ... 465771 files and directories currently installed.) Preparing to unpack .../libzbar0_0.23.92-7+deb12u1_amd64.deb ... Unpacking libzbar0:amd64 (0.23.92-7+deb12u1) over (0.23.92-7) ... Setting up libzbar0:amd64 (0.23.92-7+deb12u1) ... Processing triggers for libc-bin (2.36-9+deb12u4) ... [...] - Stefan