It was in /var/lib/apport/coredump

The bt full of gdb seems to indicate that systemd chokes on a unit file. I bet it is clamav-freshclam.
I am going to reboot now.

(gdb) bt full
#0 0x00007fec4596675b in kill () at ../sysdeps/unix/syscall-template.S:120
No locals.
#1 0x000055d907cfab1c in crash (sig=11) at ../src/core/main.c:257
sa = {__sigaction_handler = {sa_handler = 0x0, sa_sigaction = 0x0}, sa_mask = {__val = {0 <repeats 16 times>}},
sa_flags = 0, sa_restorer = 0x0}
pid = <optimized out>
__func__ = "crash"
__PRETTY_FUNCTION__ = "crash"
#2 <signal handler called>
No locals.
#3 0x000055d907d74d73 in unit_active_state (u=<optimized out>) at ../src/core/unit.c:830
__PRETTY_FUNCTION__ = "unit_active_state"
#4 0x000055d907d84d86 in unit_may_gc (u=0x55d908ddfa00) at ../src/core/unit.c:392
state = <optimized out>
r = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
__func__ = <optimized out>
#5 0x000055d907d739fe in unit_may_gc (u=0x55d908ddfa00) at ../src/core/unit.c:389
state = <optimized out>
r = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
__func__ = <optimized out>
_found = <optimized out>
__assert_in_set = <optimized out>
_error = <optimized out>
_u = <optimized out>
_l = <optimized out>
#6 unit_add_to_gc_queue (u=0x55d908ddfa00) at ../src/core/unit.c:468
__PRETTY_FUNCTION__ = "unit_add_to_gc_queue"
#7 0x000055d907d85ab1 in unit_clear_dependencies (u=0x55d908da3000) at ../src/core/unit.c:555
other_deps = 0x0
other = 0x55d908ddfa00
deps = 0x55d908dc4878
__PRETTY_FUNCTION__ = <optimized out>
#8 unit_free (u=0x55d908da3000) at ../src/core/unit.c:698
slice = 0x55d908cb92a0
t = 0x0
__PRETTY_FUNCTION__ = <optimized out>
#9 0x000055d907d45d05 in unit_free (u=<optimized out>) at ../src/core/unit.c:654
slice = <optimized out>
t = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
__unique_prefix_i15 = <optimized out>
j = <optimized out>
j = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
#10 manager_clear_jobs_and_units (m=m@entry=0x55d908cb78f0) at ../src/core/manager.c:1421
u = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
#11 0x000055d907d4b01a in manager_clear_jobs_and_units (m=0x55d908cb78f0) at ../src/core/manager.c:1418
u = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
#12 manager_reload (m=0x55d908cb78f0) at ../src/core/manager.c:3826
reloading = 0x0
fds = 0x7fec45112ba8
f = 0x55d908f6c940
r = <optimized out>
__PRETTY_FUNCTION__ = "manager_reload"
__func__ = "manager_reload"
#13 0x000055d907cf9a7b in invoke_main_loop (ret_error_message=0x7ffd4b3057f0, ret_switch_root_init=<synthetic pointer>,
ret_switch_root_dir=<synthetic pointer>, ret_fds=0x7ffd4b3057e0, ret_shutdown_verb=<synthetic pointer>,
ret_retval=<synthetic pointer>, ret_reexecute=<synthetic pointer>, saved_rlimit_memlock=0x7ffd4b305820,
saved_rlimit_nofile=0x7ffd4b305830, m=0x55d908cb78f0) at ../src/core/main.c:1934
saved_log_target = <optimized out>
saved_log_level = <optimized out>
r = <optimized out>
r = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
__func__ = <optimized out>
_error = <optimized out>
_level = <optimized out>
_e = <optimized out>
saved_log_target = <optimized out>
saved_log_level = <optimized out>
_level = <optimized out>
_e = <optimized out>
_level = <optimized out>
_e = <optimized out>
_level = <optimized out>
_e = <optimized out>
_ptr_ = <optimized out>
_ptr_ = <optimized out>
_level = <optimized out>
_e = <optimized out>
table = <optimized out>
_level = <optimized out>
_e = <optimized out>
#14 main (argc=1, argv=0x7ffd4b305ab8) at ../src/core/main.c:2910
initrd_timestamp = {realtime = 0, monotonic = 0}
userspace_timestamp = {realtime = 1726568591653978, monotonic = 37908672}
kernel_timestamp = {realtime = 1726568553745306, monotonic = 0}
security_start_timestamp = {realtime = 1726568591655330, monotonic = 37910024}
security_finish_timestamp = {realtime = 1726568591655914, monotonic = 37910609}
saved_rlimit_nofile = {rlim_cur = 1024, rlim_max = 4096}
saved_rlimit_memlock = {rlim_cur = 65536, rlim_max = 65536}
skip_setup = <optimized out>
loaded_policy = false
queue_default_job = <optimized out>
first_boot = <optimized out>
reexecute = false
switch_root_dir = 0x0
switch_root_init = 0x0
before_startup = <optimized out>
after_startup = <optimized out>
timespan = "\000\000\000\000\000\000\000\000\000\303t\255\211[\367\r\000\000\000\000\000\000\000\000\310\375\377\377\377\377\377\377\002", '\000' <repeats 15 times>, "\002\000\000\000\000\000\000\000\006\000\000\000\000\000\000\200"
shutdown_verb = 0x0
error_message = 0x0
r = <optimized out>
retval = 1
m = 0x55d908cb78f0
fds = 0x0
finish = <optimized out>
systemd = "systemd"
__func__ = "main"
__PRETTY_FUNCTION__ = "main"
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>

_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
_head = <optimized out>
_item = <optimized out>
#10 manager_clear_jobs_and_units (m=m@entry=0x55d908cb78f0) at ../src/core/manager.c:1421
u = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
#11 0x000055d907d4b01a in manager_clear_jobs_and_units (m=0x55d908cb78f0) at ../src/core/manager.c:1418
u = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
#12 manager_reload (m=0x55d908cb78f0) at ../src/core/manager.c:3826
reloading = 0x0
fds = 0x7fec45112ba8
f = 0x55d908f6c940
r = <optimized out>
__PRETTY_FUNCTION__ = "manager_reload"
__func__ = "manager_reload"
#13 0x000055d907cf9a7b in invoke_main_loop (ret_error_message=0x7ffd4b3057f0, ret_switch_root_init=<synthetic pointer>,
ret_switch_root_dir=<synthetic pointer>, ret_fds=0x7ffd4b3057e0, ret_shutdown_verb=<synthetic pointer>,
ret_retval=<synthetic pointer>, ret_reexecute=<synthetic pointer>, saved_rlimit_memlock=0x7ffd4b305820,
saved_rlimit_nofile=0x7ffd4b305830, m=0x55d908cb78f0) at ../src/core/main.c:1934
saved_log_target = <optimized out>
saved_log_level = <optimized out>
r = <optimized out>
r = <optimized out>
__PRETTY_FUNCTION__ = <optimized out>
__func__ = <optimized out>
_error = <optimized out>
_level = <optimized out>
_e = <optimized out>
saved_log_target = <optimized out>
saved_log_level = <optimized out>
_level = <optimized out>
_e = <optimized out>
_level = <optimized out>
_e = <optimized out>
_level = <optimized out>
_e = <optimized out>
_ptr_ = <optimized out>
_ptr_ = <optimized out>
_level = <optimized out>
_e = <optimized out>
table = <optimized out>
_level = <optimized out>
_e = <optimized out>
#14 main (argc=1, argv=0x7ffd4b305ab8) at ../src/core/main.c:2910
initrd_timestamp = {realtime = 0, monotonic = 0}
userspace_timestamp = {realtime = 1726568591653978, monotonic = 37908672}
kernel_timestamp = {realtime = 1726568553745306, monotonic = 0}
security_start_timestamp = {realtime = 1726568591655330, monotonic = 37910024}
security_finish_timestamp = {realtime = 1726568591655914, monotonic = 37910609}
saved_rlimit_nofile = {rlim_cur = 1024, rlim_max = 4096}
saved_rlimit_memlock = {rlim_cur = 65536, rlim_max = 65536}
skip_setup = <optimized out>
loaded_policy = false
queue_default_job = <optimized out>
first_boot = <optimized out>
reexecute = false
switch_root_dir = 0x0
switch_root_init = 0x0
before_startup = <optimized out>
after_startup = <optimized out>
timespan = "\000\000\000\000\000\000\000\000\000\303t\255\211[\367\r\000\000\000\000\000\000\000\000\310\375\377\377\377\377\377\377\002", '\000' <repeats 15 times>, "\002\000\000\000\000\000\000\000\006\000\000\000\000\000\000\200"
shutdown_verb = 0x0
error_message = 0x0
r = <optimized out>
retval = 1
m = 0x55d908cb78f0
fds = 0x0
finish = <optimized out>
systemd = "systemd"
__func__ = "main"
__PRETTY_FUNCTION__ = "main"