only what your friends share in chronological order => bad actors can't influence what gets shown first and if a friend shares disagreeable coordinated materials unfriend
If someone shares SPAM you will see it once and then it will be below what you check the next time. You can unfriend someone that shares too much SPAM. You can report it too. There's no good way for an adversary to game an aglo that decides what to put on your timeline more often when the algo is most recent first.
Heck - the original fake news phenomenon was Macedonians (?) making websites that looked like news sites to earn click through money.
People could just do that - “spam from the poisoned well”