You can trust the software in your distro's repositories (if you run a distro with well-maintained repositories). This is because, generally only well-known software gets packaged, the packager should be familiar with both the project and the code, and everything is rebuilt on the distro's own infrastructure, to ensure that a given binary actually corresponds to the source.
It might still be possible for things to slip through, but it's certainly much safer than random programs from online.
I get you. I can never think of anything that would be interesting to post or ask in the more discussion-oriented communities, let alone choose a specific one to post in. I definitely find comments easier, as well as posting to more niche communities. I feel the scope is usually better defined there.
Would you say it's about not knowing if your post would be accepted in the community, or just finding the best place for it? If it's the latter, AskLemmy could be good for general questions, or failing that, any of the casual chat communities such as !chat@beehaw.org.
As long as your post meets the rules of the community/instance, I feel it's better to post somewhere than not at all - people can always crosspost it elsewhere if they like.