E_NOREPRO

  user@ubuntu-server:~$ lsb_release -a
  No LSB modules are available.
  Distributor ID: Ubuntu
  Description:    Ubuntu 25.10
  Release:        25.10
  Codename:       questing
  user@ubuntu-server:~$ uname -a
  Linux ubuntu-server 6.17.0-7-generic #7-Ubuntu SMP PREEMPT_DYNAMIC Sat Oct 18 10:10:29 UTC 2025 x86_64 GNU/Linux
  user@ubuntu-server:~$ getent ahosts us.archive.ubuntu.com
  91.189.91.82    STREAM us.archive.ubuntu.com
  91.189.91.82    DGRAM  
  91.189.91.82    RAW    
  91.189.91.81    STREAM 
  91.189.91.81    DGRAM  
  91.189.91.81    RAW    
  91.189.91.83    STREAM 
  91.189.91.83    DGRAM  
  91.189.91.83    RAW    
  2620:2d:4002:1::102 STREAM 
  2620:2d:4002:1::102 DGRAM  
  2620:2d:4002:1::102 RAW    
  2620:2d:4002:1::101 STREAM 
  2620:2d:4002:1::101 DGRAM  
  2620:2d:4002:1::101 RAW    
  2620:2d:4002:1::103 STREAM 
  2620:2d:4002:1::103 DGRAM  
  2620:2d:4002:1::103 RAW    
  user@ubuntu-server:~$ ip --oneline link | grep -v lo: | awk '{ print $2 }'
  enp0s3:
  user@ubuntu-server:~$ ip addr | grep inet6
      inet6 ::1/128 scope host noprefixroute 
      inet6 fe80::5054:98ff:fe00:64a9/64 scope link proto kernel_ll 
  user@ubuntu-server:~$ fgrep -r -e us.archive /etc/apt/
  /etc/apt/sources.list.d/ubuntu.sources:URIs: http://us.archive.ubuntu.com/ubuntu/
  user@ubuntu-server:~$ sudo apt-get update
  Hit:1 http://us.archive.ubuntu.com/ubuntu questing InRelease                            
  Get:2 http://security.ubuntu.com/ubuntu questing-security InRelease [136 kB]            
  <snip>
  Get:43 http://security.ubuntu.com/ubuntu questing-security/multiverse amd64 c-n-f Metadata [252 B]
  Fetched 2,602 kB in 3s (968 kB/s) 
  Reading package lists... Done

I didn't think to wrap that in 'time', but it only took a few seconds to run... more than two and less than thirty. The IPv6 packet capture running during all that reveals that it never tried to reach out over v6 (but that my multicast group querier is happily running):

  user@ubuntu-server:~$ sudo tcpdump -i enp0s3 -s 0 -n 'ip6 or icmp6'
  tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
  listening on enp0s3, link-type EN10MB (Ethernet), snapshot length 262144 bytes
  22:16:44.327503 IP6 fe80::5054:98ff:fe00:64a9 > ff02::2: ICMP6, router solicitation, length 16
  22:17:35.823917 IP6 fe80::<REDACTED>          > ff02::1: HBH ICMP6, multicast listener query v2 [gaddr ::], length 28
  22:17:41.706930 IP6 fe80::5054:98ff:fe00:64a9 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28

I even manually ran unattended-upgrade, which looks to have succeeded. Other than unanswered router solicitations and multicast group query membership chatter, there continued to be no IPv6 communication at all, and none of the messages you reported appeared either in /var/log/syslog or on the terminal.

  user@ubuntu-server:~$ sudo /usr/bin/unattended-upgrade
  user@ubuntu-server:~$ sudo grep -e 'Tried to start delayed item' /var/log/syslog
  user@ubuntu-server:~$ 

What am I doing wrong?