I've looked a bit deeper and this is what happened: the package tor-0.4.7.13 has been built 2023-01-12 at this point bookworm still was testing and in January bookworm/testing had libzstd-1.5.2
but then libzstd-1.5.4 entered bookworm/testing 2023-02-23 so tor would have needed a rebuild as there is a runtime test to avoid version mismatch. Hiding a test result that checks for version mismatch is NOT a solution in case of version mismatch. Rebuilding and by that linking with libzstd-1.5.4 is. I'v seen meanwhile you've built 0.4.8.5 but put it into testing and backports only. for bookworm/stable the problem still exists. Plus there was a bug fix release, 0.4.7.14 in july "This version fixes several minor bugfixes and one major bugfix" https://forum.torproject.org/t/stable-release-0-4-7-14/8493 but for bookworm/stable the problem still exists. Even in case 0.4.8.5 doesn't fit into debian rules for stable repository, the upstream 0.4.7.14 is a pure bug fix 3305 out of 7846 tor nodes still use 0.4.7.13 - I guess most of these just because they trust in debian stable is well maintained. Please do :)
