If you find a bug in the live server installer, we might ask you to test the latest version of subiquity if we believe it has been fixed there. If you have internet access from your system this is fairly easy: boot the installer as normal, switch to tty2 once subiquity has started and run “sudo snap refresh --edge subiquity”. The latest version of subiquity will be downloaded and the installer will restart so just switch back to tty1 once the command has completed.
If you can’t switch to another tty (for example, talking to the server over the serial line), you can boot with subiquity-channel=edge on the kernel command line. Then the installer itself will offer an upgrade. Accept this and the new installer will be downloaded and installed.
If you do not have access to the internet access from your server, things are a little trickier. The subiquity source https://github.com/CanonicalLtd/subiquity contains a script
./scripts/make-edge-iso.sh which can be used to make a new ISO file containing the latest subiquity, which can then be dd-ed onto install media in the usual way.