There are quite a few Starfield side quests, otherwise known as activities, that players can find and discover. So many that most players will most likely never encounter them all. In fact, in a comparison to previous titles such as the 2011 title, Elder Scrolls V: Skyrim, there was over 270 quests in total. As Starfield is a more newer title. Releasing 11 years later, we can probably expect a lot more.
Here is a list of those that you can encounter. Plus how to unlock and complete them. These quests will include those that are part of the factions such as the Crimson Fleet and UC Vanguard. As well as those that are simply tied to the specific area.
LIST OF STARFIELD SIDE QUESTS ACTIVITIES
NEW ATLANTIS QUESTS ACTIVITIES
UC VANGUARD FACTION QUESTS
Supra Et Ultra (Join the UC Vanguard)
CRIMSON FLEET FACTION
Rook Meets King (Join Crimson Fleet)
FREESTAR RANGERS FACTION MISSIONS
Deputized (Join the Freestar Rangers Faction)
RYUJIN INDUSTRIES MISSIONS
Back to the Grind (Join Ryujin Industries Faction)