Playnite

Wait Linux doesn't have this??!! Why the fuck not?

USB support is bare bones. Always has been. Been feature requests in the core for decades.

Not much really. Maybe being able to download random exes for silly shit, but I could always spin up a VM for that.

Bluestacks for me :(

I miss my computer's performance being held hostage by "Active Protection" feature of Virus scanner!

From macOS: that the basics in UI are so much more consistent and just work. For example shortcuts across apps. This makes me insanely productive.

roblox (i miss it only a bit)

AutoHotKey

The lack of a good cad software (fusion 360), and no, freecad and openscad are not worthy equivalents.

Effort free gaming on Windows

I'll acknowledge that gaming is much better than when I entered the field 20 years ago,

but it was so nice being able to just install a game and have it function instead of install a game and play the 50/50 gamble of whether or not it's going to have some bug that forces me to go online and search the issue.

Proton DB has been a lifesaver for most issues that have occurred, but there are still so many games that have obscure problems that while not all of them prevent you from playing at all, a good portion of them have issues with them that dampen the gaming experience.

And as a bonus one, the lack of a decent Android emulator. I have tried so many different emulators for Android, and all of them work notoriously worse than BlueStacks did on Windows and a lot of times take up double the space it did. As a person who plays a lot of mobile games that require constant looking at, it was so much easier to just have it running in BlueStacks on the third monitor and then just look at it when needed

iTunes is probably the biggest, people with iDevices have a harder time with GNU/Linux

I only miss Musicbee on Windows. I've created an offline Windows VM for that one single program.