With a GUI you also don't know what it does. Its the same situation, you just click a button that runs the code instead of copying and pasting the code in the terminal. (And I would say the latter is safer because it is more transparent (for those who want to figure it out)).
Yes I second all of this. If you dont want to self-host, Nextcloud hosted on some external server is the way forward. Nextcloud is incredibly versatile. It's my music collection, photo collection, agenda, contacts, file sync, location tracker and much more.
For me Mastodon is still growing and getting more interesting, with more and more formal institutions joining (newspapers, NGOs, government institutions etc.).
Thank all the gods that there still is some serious journalism that keeps track of this, in a thorough and transparent way.