To install something you have to install it from the repository, and not download something from some webpage.
Ah yes, i should have known better than to rely on the documentation of the website of an application i should install. Do you guys really consider this a sane ecosystem? I google what kind of apps there are for what i want. I find the site of one i want to try, it says “here is a deb package for ubuntu”, and then hell ensues. And when i share this experience your reaction is “you should have known better” O_o… yeah no. This is just insanity. If according to you even the developers of applications fail to send their users in the right direction on how to get their application installed, there is probably little hope for a mere user like me.