iMac Retina 5K 27" 2017 model with Big Sur OS and external drives available.

I have downloaded/ verified the ISO I have used Etcher to create an installer USB and a CD.

Both boot up using the option boot to select process NIETHER gets me the Try-or-Install splash screen --- just a fleeting blue icon followed by scrolling script.

(side note, same behavior with Ubuntu ISO)

I'd really like to try out a Linux OS!

Screen pictures

2 pix to show boot

  • iMacs can be tricky at times. Are you using a wired keyboard and pointing device? The wireless ones will not work until after installation and some configuration. You also need to boot from an “off” state. Rebooting from macOS to the installer does not always work.
    – matigo
    Oct 26, 2021 at 22:17
  • Matigo: Wired keyboard and mouse. The "Off" state boot (instead of my usual "Restart") made no difference. –
    – OldBored
    Oct 27, 2021 at 21:56


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