There are some more obvious things you should do (in order):

1. Have backups. You are running software all the time that can corrupt your files either maliciously or, more likely, accidentally. It doesn't really matter where it comes from,

2. Get into the habit of running things in sandboxes. You don't need anything magical here, a separate (unprivileged) user account is a good enough sandbox for many things. I outline an approach for installing Calibre like this on my blog[0] (the official site uses the `curl ... | sudo sh` pattern!)

You could do more clever things like using bwrap[1] to isolate things, or use a distro designed for this kind of thing. Be aware if using a separate user account that your home directory might still be readable so if you're worried about privacy check that, or use bwrap so it's not exposed at all.

[0] https://blog.gpkb.org/posts/calibre-rootless-install/

[1] https://github.com/containers/bubblewrap