Installing packages on your distro is very easy, either via a simple command like `apt install <package>` or via a graphical appstore-like interface to the same thing. All major distro package managers are very mature and reliable.
Distributing software through those repos as a developer is not very easy, but it's not required either. If you want to distribute your app to all Linux distros without worrying about compatibility, and without requiring your customers to use the command line, you can use something like [App Image](https://appimage.org/), which is basically the same concept as [App Bundles](https://developer.apple.com/library/archive/documentation/Co...) on Macs.
There are also a lot of (less good) alternatives to App Images, like [Flatpack](https://flatpak.org/) and [Snap](https://snapcraft.io/).
If you want something fancier, you could go with something like [Guix](https://guix.gnu.org/) or [Nix](https://nixos.org/explore.html) if your customers are developers or otherwise technical.
If you want to get less fancy, you could distribute your binaries with an install script that detects the current distro/version and downloads dependencies using the installed package manager.
And if you're a user who just wants to download stuff on their computer, you just need to follow the instructions from the provider. It usually involves one of the methods above.
