Linux

sudo synaptic for a graphical package manager.

Otherwise, just use sudo apt-get if the program you want isn't there, you may need to download the source and compile it yourself

People here saying you can just download and run the .deb just like the .exe

Aren't you forgetting the "add +x permission" step?

Not specific to Mullvad, but you can use flatpak or your distro's package manager (probably apt) to install programs, On Ubuntu, you can open the software program and search the programs to install it, that should be the first thing to do when you want to install something rather than going to the website.

my tactic if the site looks trustworthy is always:

• find the explanation for the distribution I use
• ignore literally all the text
• just copy paste and execute everything that looks like a command in order in the terminal works like 8/10 times

Open the terminal and copy and paste the commands found in their install guide for Ubuntu:

# Download signing key 
sudo curl -fsSLo /usr/share/keyrings/mullvad-keyring.asc https://repository.mullvad.net/deb/mullvad-keyring.asc

# Add the stable repository
echo "deb [signed-by=/usr/share/keyrings/mullvad-keyring.asc arch=$( dpkg --print-architecture )] https://repository.mullvad.net/deb/stable $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/mullvad.list

# Install 
sudo apt update
sudo apt install mullvad-vpn

More or less: yes.

It's copy and pasting 5 lines into the terminal and hitting enter. It's not that hard. If it's not worth the 15 seconds of 'work' you probably don't need the software that badly.

And it's not the default. Usually you shouldn't add random software sources and download software from some websites. Your Linux package manager should be the source for software. (Software Manager / Store / Synaptics, ... whatever Ubuntu calls it) It installs software with one or two clicks with the mouse, the software there is tested and tied into the rest of the systems and tens of thousands of packages are available. No malware guaranteed, and updates are handled automatically.

And with other Operating systems it's also ridiculous: You need to find the website of some software, avoid malware and copycats that advertise similar software with ads, click download, click 'yes' I accept a download with a harmful extension. Then you need to open the file manager and double click on it. Then a window opens and you need to click 'next'. Accept the terms. Give permission to install and maybe remove a few ticks and choose a location. I'd say it's about the same amount of work and the downside is it doesn't necessarily handle updates and security fixes.

I think Ubuntu doesn't have Mullvad available in their own repository. I took another approach and imported their settings/profile into the VPN/network manager that is available per default on many Linux distributions. No install required at all. But importing the settings isn't easier, so YMMV here. And I think you have to create a profile for each and every country/endpoint which is a bit cumbersome, depending on what you're trying to do with the VPN.