AKA you are trying to install Raspberry Pi OS Lite headlessly, yet someone didn't include the service file responsible for enabling SSH.

1. Mount the medium:

   # Find which device corresponds to the card:
   lsblk
   # Make a mount point:
   mkdir /mnt/ext01
   # Mount, use device ID from earlier:
   mount /dev/<device> /mnt/ext01
   

2. Link the service file (the link is relative to the path on the mounted medium):

   ln -s /lib/systemd/system/ssh.service /mnt/ext01/etc/systemd/system/multi-user.target.wants/ssh.service
   

3. Unmount the medium:

   umount /mnt/ext01
   

4. Return the medium into the correct device
5. Boot and hope for the best