For instance, I run qemu all the time to emulate various android devices.
I suspect that you're thinking specifically of game emulation though.
Running software on an emulated device is fine legally as long as it doesn't violate copyright law.
For instance, you can legally backup software that you own in the US [1] - that extends to games as well - and because emulators themselves are legal (although you may also need to backup the device's BIOS), you can have a completely legitimate archive of copyrighted games to run via an emulator.
That said, it's unlikely that most people archive software themselves, and it is not legal to distribute backups in the US, even if both parties have legitimately acquired copies of the source material.
Torrenting is a pretty standard, official, way of distributing Linux ISOs. Linux' license also doesn't really stop anyone from doing so, as it very much wants its users to share it with others (GPL v2, see the 4 freedoms of the FSF). There could be problems distributing e.g. Red Hat-owned stuff (trademarks, copyrighted things, non-FOSS software and such) without permission, but Linux itself is completely legal to share.
Torrenting also isn't illegal by itself or a direct link to pirating, it is just a very common way of sharing pirated data.
No, in the way that advertising that your product can play a few homebrew games when it already can play thousands of Steam games makes no sense. It's obviously to hint at playing Nintendo titles.
Why does that matter? It's like torrents and Linux distributions, perfectly legal, it's not the software developers intent that makes the file sharing be legal or not, it's the users usage of such software.
1. Then you don't have to carry a steam deck and a switch.
2. This way you can buy physical copies of games, keeping full control and the ability to resell them, while also carrying your current game library on an SD card.
Edit: I forgot modding! That's a huge use of emulation.
So you don't have to travel with both your Switch and your Steamdeck. So you can play games at higher resolution and fps than the Switch. So people can make playthough and tips/tricks videos of Switch games without needing to buy a capture card. So you can use game mods without jailbreaking your switch.
For instance, I run qemu all the time to emulate various android devices.
I suspect that you're thinking specifically of game emulation though.
Running software on an emulated device is fine legally as long as it doesn't violate copyright law.
For instance, you can legally backup software that you own in the US [1] - that extends to games as well - and because emulators themselves are legal (although you may also need to backup the device's BIOS), you can have a completely legitimate archive of copyrighted games to run via an emulator.
That said, it's unlikely that most people archive software themselves, and it is not legal to distribute backups in the US, even if both parties have legitimately acquired copies of the source material.
[1] https://www.copyright.gov/help/faq/faq-digital.html