Change keyboard layout when booting Ubuntu 18.04 live cd/USB in UEFI

I’m selecting the Finnish locale and keyboard layout here, YMMV.

1. With the Try Ubuntu option selected, hit ‘e’ to enter the boot parameter editor
2. Go to the end of the line with linux kernel boot parameters (they perhaps end with quiet splash --) and add these parameters: locale=fi_FI console-setup/layoutcode=fi (so that, if the previous example holds, it now ends with quiet splash -- locale=fi_FI console-setup/layoutcode=fi)
3. Hit Ctrl-x to boot