Linux

In Cinnamon you can assign the shortcut for this. It is just not defined. You can go to Settings->Keyboard->Windows and you should look for something like Positioning (I am trying to translate in English what I see). You assigned the shortcut you want and that's it

Its not exact but KDE Plasma has the drag to the corner and get the same quadrant/full screen when you drag to the top middle.

by the sounds of it if you are using Gnome add the Put Windows extension. then you hit Super+ Keypad number for the screen corners. i.e. top right is Super+kp9

rectangle is a built-in feature of the KDE plasma desktop lol

It seems you've chosen a DE that is not particularly well-suited to this task. Cinnamon is meant to be simplistic, and offer an easy transition from Windows with its Windows-like layout. It is purposefully less customizable than many other DEs. I second the recommendation of KDE Plasma, as this is actually available as a shortcut without any extensions, but if you wish to customize your DE deeply like this, KDE is incredibly customizable. You can do essentially anything you want in it and get it to look however you want.

Since you said that you're trying out Mint, now would be a good time to switch distro so you don't get attached to something that doesn't suit your needs. Switching desktop environments can cause lots of issues, so it's often best to just pick a distro with the DE you want. My personal recommendation is Fedora's KDE spin (though there are discussions of Fedora's default workstation switching to KDE in the future). If you're invested into Debian, then I don't really have any experience with Debian-based KDE distros, but I'm sure someone else could recommend you something. To be clear, the benefit of recommending Mint as a starter distro has gradually diminished as other distros have become more user-friendly. Fedora is a perfectly fine distro for someone new to desktop Linux (especially since you're already experienced on the command line); you'll just have to look up how to install Nvidia drivers if you have an Nvidia graphics card. AMD commits their driver to the Linux kernel, so no need to do anything if you have an AMD card. Try out some distros in a VM before you commit to anything though; it's much less commitment than installing so it's far easier to test distros out and see what best suits you.

System Settings > Keyboard > Shortcuts > Windows

Although I just skimmed the Rectangle front page, I think this about covers everything you're asking for in Cinnamon...? The default shortcut is Super/Win-arrow.

same boat. was on GNOME and used gTile over there; once the (cumbersome) setup was done, worked as expected, especially the cycle function (cycle between 1/3, 1/2, and 2/3 on repeated keypresses).

now I'm on Plasma and there isn't anything worthwhile; tried a couple of solutions but most of those are of the auto-tile kind where the WM "guesses" what you want and then you adjust it, which is beyond asinine to me. I have a huge screen and I want to send this window do this quarter and this to this sixth and this to half and so on.

anyhow, none have what I need, so I learned to live without it.

edit: found the exact one I needed - Better Quick Tiles for Plasma 6. does exactly what I need, including alternating between 1/3, 1/2, 2/3.

It's a window manager feature. I don't know which one is used in Cinnamon by default and if it is able to do so, but you can switch to another one anyway even without changing the complete DE. E. g. xfwm4 provides such a feature. I believe that kwin also does.

I also suggest you to try some tiling WM, you may like it.

What Desktop are you using? GNOME and KDE, as well as prealpha COSMIC and probably more support this out of the box.

Hiprland? Although Wayland has some quirks

As a primary Linux user who wrote his own X tool to do exactly this and has been missing this functionality on Mac - thank you!

I'll send my unpublished code your way soon. It's just Go, relying on the WM (run command shortcuts) to call it. Move+Resize and Focus functionality.

It won't work on Wayland, which seems to require native compositor support - labWC is halfway there.

edit: check your PMs

I also use Linux mint with cinnamon... Is this not just the Ctrl + Fn + arrow key? I think that's it, or maybe shift (not at my computer to check). Either way, I use this all the time to fit windows either on 50% of the left or right, or in one of the 4 corners. For example, if I want it in the top right, I just use the hot keys and target right then up.

I am not a KDE user but it sounds like KDE would be great for you. KDE should let you customize your desktop a ton including keyboard shortcuts

Have you given any thought to using a window manager with your desktop environment? Maybe one that can be customized to provide very basic functionality? I use bspwm with XFCE, for example.

It’s funny. I have been forced to use macOS because of work, and I use rectangle to mimic what KDE plasma does out of the box. I’d suggest using KDE if you wanted something powerfully customizable and user friendly. If you find something that works with other windows decorations (non-KDE), I’d love to know about them too for when I inevitably switch back to Linux Desktop!