Can I start with Gentoo or is that too easy?

I would say that security and privacy are also very important. That’s something you can’t get with Windows.

Congratulations! Next you might want to learn about the Free Software movement: https://youtu.be/Ag1AKIl_2GM

So, yeah, sell me on Linux, please.

Windows has spyware, so that should be enough reason to not use it for someone like you. You will have to spend some time to learn GNU/Linux, but for most office tasks it shouldn’t be difficult, especially if you are good with computers. Most popular distros already come with a PDF viewer and Libre Office, so it should be able to do almost everything you want out of the box. VLC player can play all common video types and is easy to install. Libre Office might have issues with some Word documents though, so you might need to look into that. A web browser (usually Firefox) and probably some email client will be preinstalled as well.

You might need to check if your printer and scanner will be supported out of the box or if extra drivers from the manufacturer are needed (then check if they are available on their website). I think printers will probably work fine out of the box, but scanners might require extra drivers (this depends on the model - there are models that don’t).

If you need more motivation, look into the Free Software movement: https://youtu.be/Ag1AKIl_2GM

GNOME also has an app that lets you do encrypted incremental backups very easily.

Even The Linux Foundation has a twitter

Because Linus Torvalds doesn’t care about the Free Software movement and user freedom. It’s why his kernel is still on GPL2.

You think it was just a fake promise? I haven’t thought about it, but it’s certainly possible.