Is it possible to avoid the missions to kill the Lieutenants?
I heard that the player is forced to complete the Lieutenant killing missions upon getting enough resistance points, but is that true?
The Wiki notes the minimum thresholds to start missions, but only implies that they're forced upon the player?
it is forced, every side activities you completed (clearing outpost, doing side-missions, etc.) will fill the "resistance point" and once it's full you'll be forcefully abducted into a cutscene and the story for that lieutenant will progress.
this is the major difference in FC5 story approach.
if you're playing on PC, there are mods to make this "resistance point" fills more slowly