Since you confirmed
openssh-server is installed, the issue is almost certainly a configuration block or a systemd conflict specific to Ubuntu 22.04 LXC templates.
Follow these steps from the container's console:

1. Enable Root Login -> Ubuntu 22.04 blocks root login by default. 

Edit the config: 
```
nano /etc/ssh/sshd_config
```

Find the line: 
```
#PermitRootLogin prohibit-password
```

Change it to: 
```
PermitRootLogin yes
```

Save and exit (Ctrl+O, Enter, Ctrl+X).