Where does Ubuntu (or Linux in general) install its applications?

Question

In Windows, all installed applications go into the Program Files/Program Files(x86) of the hard-drive in which the application is installed on.

What is the equivalent in Linux or Ubuntu specifically?

When I install a program using APT, flatpacks, snaps or using manual methods such as .deb among others - where should I be installing these? Or do these methods automatically follow a convention?

Additional small question: Does the same convention apply to servers?

Answer 1

Packages, whether on a Server or Desktop edition, generally follow the Filesystem Hierarchy Standard of the Linux Foundation which has an illustrated overview at https://www.howtogeek.com/117435/htg-explains-the-linux-directory-structure-explained/ . Appimages, flatpacks, and snaps may deviate further from the standard than do apps installed through apt.