Fucking NeoFetch made you this hormonal, dude?
Okay, look, package managers area really handy, but they're handy enough to forget that there are other ways to install software on a system. Usually you can find the project's Git repo and there will either be an INSTALL file or an install section in the README which will guide you through how to compile and install it. You might have to install dependencies first and do some annoying compilation steps but, at least for well-documented software which was written with an eye for broad compatibility, it's usually not that hard. In NeoFetch's case, since it's just a Bash script, you should be able to just
clone the repo and then move the script into a $PATH directory.
As for your other example with the .so file, that's probably more complicated, but we're still talking about a FOSS OS so whatever version of the file you're looking for should be out there somewhere.