I don't miss anything really. All of my software already worked.

A minor but useful GUI feature on MacOS in list view is showing the size of directories as well as individual files and being able to sort by those sizes. That extra step in Linux of having to contextually click on a listed directory and choose "Properties" all the way at the bottom of that menu is a minor annoyance

For me it’s the Mac Finder. It’s always running so (unless it crashes) there’s no delay in opening a file manager window and, more importantly, it has built in Quicklook and Miller columns. Haven’t managed to find a good-enough implementation of either of those in Linux, so I just work around it.

Desktop session restore. Shut down pc, turn back on, everything like when shut down. Or on crash, sometime even kernel panic, restart and right back to work.

Nexusmods.

Being able to sync music or movies to my iPhone/iPad. More of an Apple issue than Linux, yet Mac/PC is compatible.

VLC does work, but since it’s not how Apple wants you to use your device it’s not as convincing nor flushed out.

I missed Odin 3 for a few years until I switched to Graphene and never looked back. In tried the FOSS package it didn't work for me and the documentation was beyond my skills at the time.

I miss the stupid people comradery, sometimes. People act funny when you're a normal stupid person and use Linux without the hoodie and a Matrix screen saver.

Support for auto cloud sync from vendors, or just auto cloud sync of setting between devices.

DE stability. I keep a Mac around for times when Gnome is kind of broken.

cmd shortcuts which don’t interfere with app shortcuts.

Powerful desktop Arm chips.

Gui to manage services.

Gui to manage firewall.

Easy fleet management tools.

A real terminal services and Remote Desktop solution.

Desktop icons.

Tighter userland security.

Tighter OS security. Mostly dm-verify and fs-verify.

Tiling support. (There are extensions, but I need to experiment.)

Not having to recompile out of tree kernel modules after a kernel upgrade.

Base and extras being cleanly separated.

I miss RDP.
Preinstalled in every Windows, just allow access on the host with one click, open it, type in the IP of the remote host, and it's like you're on that pc. Sound, mic, camera, other devices, multiple screens, ... It generally just works.

On Linux with Wayland, I don't even know how or if it works, or how to set it up on the host machine.

Edit: OK, it isn't that difficult, actually:
https://std.rocks/gnulinux_rdp_remotedesktop.html#Windows

Game pass

Hardware info (hwinfo) or similar. Be able to check all voltages, speed and temps while testing new hardware. For example my ARC A770 has little to no info, and shows running at pcie x1.

Edit: mistakingly thought link width was x4, but looking at it again shows x1

Bansi Buddy and NetZero of course!

But really it's winamp, which of course I would still use on Linux except I've become a disciple of the streaming gods.

I'm honestly surprised that nobody has said anything about MS Office, but it's not like I expect anyone to miss the application itself, it's just that if your work requires you to interface with it, there really is no alternative to running Windows or MacOS. Microsoft's own Office Online versions of the apps do a worse job of maintaining DOC/PPT formatting consistency than the possible Russian spyware that is OnlyOffice, which also screws things up too often to be relied upon. LibreOffice is, let's be honest, a total mess (with the exception of Calc, which also isn't consistent with the current version of Excel, but can do some things that Excel no longer can do, so I appreciate it more as a complementary tool than as a replacement).

I play and mod a lot of older games most of which aren't on Steam, so getting some of them running takes a bit more manual effort especially if they require a 3rd party patch to run on modern hardware.

Normally it's pretty simple like declaring some extra DLL files, But sometimes I'm jumping through hoops trying to get some old installer than hasn't been updated since 2009 to run...

I've had more success than failures though, Wine is pretty amazing imo.

Not something I use personally, but a super easy, #JustWorks kiosk mode.

It's the only thing I think Windows does better than Linux.

Don't get me wrong, you can turn Linux into a great kiosk device, but it takes a lot of technical labor.

In the IT space, I often need to set up a basic kiosk device for HR portals, safety training stations, etc. In Windows, this takes 5 minutes tops.

If I had the programming chops, it would be my #1 project to work on. Even if it only worked with a specific DE or distro, I would be alright with that, as long as it was as easy and quick to set up as Windows Kiosk mode.

I miss the human connection with those around me who use windows. After years of using Linux almost exclusively, I now miss being able to relate to them. Sometimes I feel lonely because of it.

Colleagues get to resonate with all the windows slowness and reliability issues, and I can only stay silent.

"Hey, how can I do this obscure thing?" "Oh yes that's easy... err... no, I don't know." So many methods that are easy on Linux are basically impractical on windows. E.g. many text file processing tasks are doable swiftly with simple shell scripts or even bash one-liners; what will a windows user do? Telling them to automate something means suggesting them to create a new Java project. Opening an SSH session means using Mobaxterm which limits the number of sessions you can create.

I miss all the crashes, the blue screen of death, the automatic updates that reconfigure all the personal changes you made to try make Windows work better, and all the hunting around for cracked proprietary software.

Foobar2000. Haven't found anything similar in terms of ui customization options, easy convert and ReplayGain operations built in.

Ive been mostly on linux for like 25 years, but i was using a chromebook for a while bc it was cheap (had a linux desktop tho).

I miss easily running android apps on my laptop. I could install waydroid but its not that big of a deal to me. Just the only thing i could think of that i miss from another os...

When I was using Windows, I used Adobe Lightroom with the Negative Lab Pro plugin to digitize my film negatives. I've played around with Darktable, and it does the job, but it's a lot more fiddly, and it discourages me from processing film.

There was a lot more I missed when I switched, can't think of anything now. I was going to joke that I miss being 19. But eh, I'm doing better now than I was then.