just some recomendations i have for good linux apps

Screen Savers
1. pipes.sh: a screensaver showing a line randomly moving around the screen, leaving a trail behind it

Installation
just download and run
or if you use homebrew: 
brew install pipes-sh
dependencies: ncurses (for tput) 
sudo apt-get install libncurses5-dev libncursesw5-dev || sudo yum install ncurses-devel || sudo dnf install ncurses-devel
2. cmatrix: a screensaver showing a marix likeanimation

to install: see the github

gif of cmatrix gif of cmatrix
3. asciiquarium: a screensaver showing an aquarium

Installation Fedora: 
sudo dnf install asciiquarium

Arch Linux: 
sudo pacman -S asciiquarium

PPA: 
sudo add-apt-repository ppa:ytvwld/asciiquariumbr
sudo apt update
sudo apt install asciiquarium

gif of asciiquarium gif of asciiquarium
Tools 1.ffmpeg: a popular file conversion tool.
to install: Ubuntu 18.04: 
            sudo apt-get install software-properties-common; 

            sudo add-apt-repository ppa:mc3man/trusty-media; 

            sudo apt-get update; 

            sudo apt-get dist-upgrade; 

            sudo apt-get install ffmpeg

Debian 9 & Ubuntu 20.04: 
sudo apt install ffmpeg

Debian 8: run 
sudo vi /etc/apt/source.list
and append 
            # deb-multimedia 

            deb http://www.deb-multimedia.org jessie main non-free 

            deb-src http://www.deb-multimedia.org jessie main non-free
Save the file by pressing ESC and close the file by pressing : and q then run 
                sudo apt update 

                sudo apt install deb-multimedia-keyring 

                sudo apt update 

                sudo apt install ffmpeg
2.inkscape: a useful coreldraw alternative.
>to install: visit the wiki Ubuntu & Debian 
            sudo apt-get update 

            sudo apt-get install inkscape

Ubuntu (if above didnt work) 
                sudo add-apt-repository universe 

                sudo add-apt-repository ppa:inkscape.dev/stable 

                sudo apt-get update 

                sudo apt install inkscape
3.gimp: GNU Image Manipulation Program.
to install: Ubuntu/Debian: 
sudo apt install gimp
Fedora: 
sudo yum install gimp
CentOS/RedHat: 
sudo dnf install gimp
Arch: 
sudo pacman -S gimp
4.flatpak: a package manager.
to install: visit the official site
5.fish: the friendly interactive shell
to install: visit the official