LinuxMint really spoils me. The fact that you can double click a .deb file and it launches an installer just like a Windows .exe is *chef's kiss*
Anything to keep me out of the CLI is a win in my book. And dramatically lowers the barriers to entry for the #LinuxCurious and #Endof10 crowd.
Sorry but I have to stress that this is a big antipattern that should not be promoted.
Having "Appstores" and package managers is a good thing. It is extremely insecure and unreliable to hunt unverified and unmanaged executables on the web.
Always install software from repositories, using the terminal or any appstore you like. If that isnt there, see if #Flathub has it.
If you still dont find it, the maintainers should have a repo and #PGP key. It is installed to the system and the package manager will then find it.
It will only install packages if they are verified, and updates will be automatically applied with the rest of your system.
Please, dont install random .deb files. They have no verification and no updates.
Some exceptions like #Vivaldi exist and setup the repo at first run. But that is weird and still less secure.
See, you might need to use a terminal as the packages might not have #Appstream metadata.
But often packages will appear in your appstore.
And otherwise, what is so "gatekeepy" about entering a few commands?
I can explain what they do:
1. Write a file to the system including URL where to get packages
2. Download the PGP public key used to verify the packages
3. sudo apt update (update the package repos)
4. apt search packagename (get the exact name)
5. sudo apt install packagename
JL Johnson 
Henning