Everyone - thank you - all of you - for indulging me and for the humour along the way!

I've really enjoyed the suggestions (many of which I've never heard of!) and your reasoning. I've thought about my intentions and the spare machine really is just that so I won't be installing something with the view to make it permanent. I will be a fun thing, a chance to learn - a chance to play about without worrying what if it all goes wrong. And as someone mentioned - yes I will be wiping it and trying something else once I think I've got sufficient from each installation.

Again, thank you!

You are welcome! Best of luck! Have fun!
Also, to make things easy I might grab a USB stick and load it with Ventoy or E2B and copy on the ISO for each of the distributions you want to try. That way you can just reboot into the USB and select the one you want to try at that particular time. If you use images that will run in Live mode before installation, you can even give them a look and try before you write to the main drive.

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You're welcome. I would caution that each distro needs some sorting, perhaps finding your hardware, getting online, choosing preferred defaults, mastering the individual package manager and raiding the repositories. Then your experience begins.

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Both of you - thanks! I really appreciate the advice and the Ventoy E2B looks seriously interesting and useful! I'd never heard of either - of course.