I faced a situation where the console output was obviously not complete:

----------%<-------------------%<-------------------%<-------------------%<-----------
...
1 running 'modules:config' at Mon, 07 Dec 2020 17:56:42 +0000. Up 151.67 seconds
.
Ý  151.801402¨ cloud-initÝ2068¨: Set the following 'random' passwords
Ý  151.801442¨ cloud-initÝ2068¨: installer:qDWRj7PSNdDRHa5Hgx2C
Ý Ý0;32m  OK   Ý0m¨ Finished  Ý0;1;39mApply the settings specified in cloud-conf
ig Ý0m.
         Starting  Ý0;1;39mExecute cloud user/final scripts Ý0m...
ci-info: no authorized SSH keys fingerprints found for user installer.
<14>Dec  7 17:56:43 ec2:
<14>Dec  7 17:56:43 ec2: #######################################################
######
<14>Dec  7 17:56:43 ec2: -----BEGIN SSH HOST KEY FINGERPRINTS-----
<14>Dec  7 17:56:43 ec2: 1024 SHA256:uYBjXvyrMNVmKqd7D37likufviobGlu3amJ7J2mDhOg
 root@ubuntu-server (DSA)
<14>Dec  7 17:56:43 ec2: 256 SHA256:m1EEaYG/QZt619PbuXOwjsb9aiTjKNQCGrl85S9uns0
root@ubuntu-server (ECDSA)
<14>Dec  7 17:56:43 ec2: 256 SHA256:/nWXhTHOH8rWQRVvkDUVP7f2BgLqAgRJgFSUGLKK6Eo
root@ubuntu-server (ED25519)
<14>Dec  7 17:56:43 ec2: 3072 SHA256:dXgLSm+Vjyi16l8/rXcH2j4Laujrgi8hB1wvCMyaSQE
 root@ubuntu-server (RSA)
<14>Dec  7 17:56:43 ec2: -----END SSH HOST KEY FINGERPRINTS-----
<14>Dec  7 17:56:43 ec2: ###################################################### 
######
-----BEGIN SSH HOST KEY KEYS-----
ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBBJAvTEU
tdx9KsFYGSUIMjGsJA2yJMNQ8uctAvWMHxsZmuKDqsmXN1K4iB/A6dkKmYCUQt7IwcOjbWDCFdUhKKU=
 root@ubuntu-server
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBTPAeVCKbRObLBoKmkCZhrJiFriElrDNGazEpqh5Poq
 root@ubuntu-server
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQC/Tirwlj7pyJvkKJcmLlP8KkPB+i9xBgcHUB093+9O
LeJJsh/VQfsXOlqNTGO0TEcO2t9eEuO9kq8hnw09R35vFLBFsyQWaGPGOOB31TBfYUhSMGjh9XZrmMc0
wG1Iw07W2F6pN4f9a89maTjlhbgqQq+tkQMumyxj4VmvJTUBTxROiiQ90Ms5M24ShPb+a2lwe40toIh0
TGATxitt62pxqZcJMbzO+OJpnJQPs6o79nczIL54zWkI818yzsara1xiYmo/FuU2T2tr6bFUIr/02PKW
zlTDpgreQXQ9UfoNRhUKKKAqgSZHMIS5jBUqj619e6HZ6kAM5fmfFRf7ZyP4nW/7ZwXfO9nHv9hJnhIO
6UAvvUFijPelIoWLilkX/S3FZv9mEs1muv8+ikKPhuL6GxgEMvGPweZzf6YkWbPGjOez5B0PWXFTRw0j
4lidShONuGn4utwuha6dJ226ym8jCxh4PMom1MChk8cFMmjY/GDxNYjSQlj/EopTfZ1vkZc= root@ub
untu-server
-----END SSH HOST KEY KEYS-----
Ý  152.164420¨ cloud-initÝ2084¨: Cloud-init v. 20.2-45-g5f7825e2-0ubuntu1~20.04.
1 running 'modules:final' at Mon, 07 Dec 2020 17:56:43 +0000. Up 152.08 seconds.

Ý  152.164507¨ cloud-initÝ2084¨: ci-info: no authorized SSH keys fingerprints fo
und for user installer.
Ý  152.164548¨ cloud-initÝ2084¨: Cloud-init v. 20.2-45-g5f7825e2-0ubuntu1~20.04 
1 finished at Mon, 07 Dec 2020 17:56:43 +0000. Datasource DataSourceNoCloud Ýsee
d=/var/lib/cloud/seed/nocloud¨Ýdsmode=net¨.  Up 152.16 seconds
Ý  152.164593¨ cloud-initÝ2084¨: Welcome to Ubuntu Server Installer!
Ý  152.164631¨ cloud-initÝ2084¨: Above you will find SSH host keys and a random
password set for the `installer` user. You can use these credentials to ssh-in a
nd complete the installation. If you provided SSH keys in the cloud-init datasou
rce, they were also provisioned to the installer user.
Ý  152.164675¨ cloud-initÝ2084¨: If you have access to the graphical console, li
ke TTY1 or HMC ASCII terminal you can complete the installation there too.
Ý Ý0;32m  OK   Ý0m¨ Finished  Ý0;1;39mExecute cloud user/final scripts Ý0m.
Ý Ý0;32m  OK   Ý0m¨ Reached target  Ý0;1;39mCloud-init target Ý0m.
Ý Ý0;32m  OK   Ý0m¨ Started  Ý0;1;39mSubiquity, the installer for Ubuntu Server
hvc0 Ý0m.
Ý Ý0;32m  OK   Ý0m¨ Started  Ý0;1;39mSubiquity, the ins   er for Ubuntu Server t
tysclp0 Ý0m.
----------%<-------------------%<-------------------%<-------------------%<-----------

The summary with the finger prints as well as the ubuntu-server login msg is missing here.

But in this case the ssh login (and the subiquity UI) works.
So maybe the logs from this system can shed some more light into this?!