This depends on which iMac it is. If it’s an Intel iMac, it is slightly easier, and if it’s an Apple Silicon iMac, it will be a bit more difficult. If it’s a Silicon, you’d need to use Asahi Linux, or have varying support. If it’s Intel, I’m pretty sure it’s similiar to installing on a PC, but can’t say for sure. I’ll look into it more

If it’s a MacBook that no longer gets updates from Apple then it’s probably from around 2014ish, and is definitely an Intel Mac. This is a great candidate for Linux. If you want an environment that is similar to Mac, go with gnome as the desktop environment. Outside of that, any of the major distributions should be fine. I’ve run KDE Neon, Ubuntu, and am currently running fedora on a 2014 iMac and all of them worked without issue.

Oh, and the person you’re helping may be better served by either the dosdude Catalina patcher or the open core legacy patcher.

Walk through your process on these with someone who’s used them first before you just go off, if you don’t have access to another device running macos then you can “soft lock” yourself.

If you’re gonna work on macs it’s good idea to have one, even what the kids used to call a hackintosh.

You need to know what you have. Other people have teased out that you have a MacBook Air, but there’s several different versions.

Apple hardware for like twenty years has used two types of naming conventions, the Trade Name (Approximate Date) and the Trade Name Number,Number designation. You might have a MacBook Air 7,1 for example which is an Early 2015. The TN N,N is the model Identifier and the TN (AD) is the model.

You can find out what you have by clicking on the apple menu in the upper left hand corner and choosing “about this mac”. The window that pops up will tell you the model and if you click “system report” you will get a ton of information that should have the model identifier somewhere near the top.

You can also look up the serial on the website everymac.com and it’ll tell you a best guess which is almost always right!

Once you’ve done that you can much more effectively search for the pitfalls of installing Linux on that computer.

There’s no such thing as an iMac laptop and you don’t say which iMac this even is…

As above; intel will be SO much easier

Macs don’t have a bios. But they boot easily into Linux (again intel)

Enjoy

I’ve installed Gentoo, fedora and Debian on powerpc and Intel Macs a couple times in my past.

The Intel Macs were no more difficult than Windows machines and the powerpc Macs required an extra step for yaboot and time to fiddle with an of the services; but still not difficult.

It would help if you got the model right, and an exact one at that. As the others said, “iMac” isn’t a mac laptop, but an AIO desktop.

I run linux on one of these. Everything worked out of the box, except for wireless. See my 2-part adventure for how I solved it.

Mac “bios” isn’t exactly how you’d expect from PCs. Hold down alt key during startup to enter boot menu, and you’re good to go.

If your family member was a mac user before, they might be most comfortable on Gnome, as it has aped many ui features from mac os. It has a similar dock, fluid trackpad-friendly navigation that works the same way, and more.

I installed EndeavourOS on a 2013 MacBook Air a month ago for a backpack trip. It was light enough to carry around and it was cheap enough I did not worry about it being broken or stolen.

It works fantastically. LibreOffice, Outlook online, Teams, OBS Studio, Distrobox, Docker, IntellijIDEA. I have even played a little Steam on it. The only thing that was not out of the box was the iSight camera and even that was a one line command after install.

The only software that let me down was DaVinci Resolve. The integrated GPU is not supported.

All I did was hold down Option at boot so I could boot off the USB and then I let the installer do the work. Anybody could do it.

Fedora has always had good Mac support in my experience. Should just be able to hold option key at boot and select the USB.

If you want to continue dual booting I’d use the Mac’s recovery mode to shrink the partition so it leaves space first. Other than that it should be just like normal. Hold option to get the boot menu.

(Just as a side reference, the “iMac” is that all-in-one computer that just looks like a big monitor on your desk that connects to a keyboard and mouse.)

Sounds like definitely Intel. Macs have EFI (Extensible Firmware Interface) rather than BIOS. Attach the install media and hold Option when powering up. This will take you to the EFI boot loader, where you should see icons for each potential startup disk. Select the Linux installer and hit Return or click the button to advance.

I don’t know which distros have the best support for different generations of Apple hardware. You should be able to get some sense of whether the distro is a good candidate from observing whether the mouse and kbd are functional before you commit to the install.

Linux runs fine on Intel Macs. There are a couple peculiarities you’ll want to be aware of, though.

• Ventoy doesn’t work as an installer. The boot menu will come up, but any ISO you choose will hang
• Not all distros will recognize the wireless card and install the firmware (Be prepared to install it using a USB to Ethernet adapter)
• Same goes for the iSight web cam

Other than those initial hiccups, everything works pretty flawlessly.

I was quite successful running EndeavourOS on my Macbook Pro 2016, but not everything works perfectly. Still, performance under Linux seems a little better.

First check what year the Mac is. If it is 2014 and below, it will be easier. If it’s over, look online for much more detailed info. Especially batery management, hybernation, wifi, etc. And make sure you can connect ethernet and external keyboard if needed during install.

I had to uninstall broadcom-wl, bc it did not work, but the default (brcmfmac) works like charm.