No, it is not funny (not even supposed to be), yet and as well you are not supposed to be left alone within this “issue”. But still, direct and only answer (link to PureOS official source/repo) to your question is provided by @wctaylor within his post #16 here. But anyhow, if your question insists on how someone can search or review which packages are available to be installed (or already installed), people used to use Synaptic (https://repo.pureos.net/pureos/pool/main/s/synaptic/) but, without recently testing this, I think it is still read-only (can’t edit) under Wayland (as default PureOS display server protocol):
Furthermore post #16 recommends typing man apt within Terminal (as I read it, includes apt-cache command too). What myself might recommend to you is to prepare yourself with man aptitude and afterwards execute something like: aptitude install --without-recommends package (as without --without-recommends you might get things installed you just don’t need), when unsure how to proceed. Now let me question myself if you ever typed: sudo aptitude and are familiar with / usage within opened aptitude screen, similar (but not functional) to Ctrl+f.
In addition to above and current, like gnome-software, or next, like Souk, upcoming GNOME flatpak app store (search for DqsmQyUk8 under YouTube), libhandy friendly (fund-this-app 
), packages overview/manager under PureOS might be someone personal choice, but answer from post #16 is the only one that shows from where main packages (non-flatpaked) are coming from (which Linux-libre repository).
And I hope this helps in terms of your orientation, toward any approach of yours (as sudo user) that you might choose (besides using current Software 3.36.1 catalog only), helps little bit (just another thought of mine, not direct answer, that isn’t didactical or tends to be find as ideal one) to understand “the link”, from above, purpose in its initial terms. And perhaps there are other easier proposals (if synaptic or gnome-software indeed aren’t adequate/perfect apps, to be used) on how-to search or install/purge, get better overview of “what’s up” (read available) PureOS apps/packages, but I’m not aware of.