Unconventional ways to get psi theory in vanilla

Psionic Theory is the gatekeeping rare tech for psi ascension. getting it normally via tech draw can be painful. luckily the game offers quite some unconventional ways of acquiring this research option. This guide provide an exhaustive list of such unconventional ways.

everything

Ordered in ease of access, from most probable to least probable.

• Teacher of the shroud origin.
  The bluntest of the all. No RNG. No anything. Available right at the start of the game.
  Remark: Can be frustrating if you choose this origin, but got zroni as precursor. Otherwise 10/10.
  
  
• Zroni precursor.
  Tech option is given twice, both on first digsite and on delve into zroni secrets.
  Free Tech Progress: 20% from digsite, 25% from special project.
  DLC: Ancient Relics.
  Remark: This is perhaps the best option.
  
  
• One outcome of Dimension portal if spiritualist.
  Dimensional Portal is one of the common colony event that has many outcomes. One of the outcome is Dimension of Suffering. Spiritualists are given the option to close the portal using psionics.
  Free Tech Progress: 80%.
  DLC: Base game
  Remark: Very RNG dependant. First you need to get this colony event (though this is not that rare), then the event must give you the right outcome. The two special project require ~12k research points and the first project is 8k. Not sure if it's worth the gamble.
  
  
• Living sea.
  A prescripted system will contain an ocean world with modifier Living Sea. The event require you to colonize the world and enact a decision. This will give you psionic theory directly (meaning you don't have to research it at all) if you don't yet have it, or telepathy if you have psi theory, or precognition interface if you have telepathy, or a heap of research if you have all of these three.
  Free Tech Progress: No.
  DLC: Distant Stars.
  Remark: More impactful at smaller galaxy size, as these guaranteed worlds are easier to be found. Does sacarifice a scientist, but an exploration oriented scientist is kind of expendable anyway. The planet is nice as a research world anyway.
  
  
• Study stone age Pre FTL Hive Mind
  Observing a stone age pre ftl hive mind will have a small chance of firing an observation event Nascent Collective every month. Event option "Retrieve the Prime for study" have a 66% chance of success, and upon success, one option you get will add psi theory as research option. This will also add 5% tech progress.
  Free Tech Progress: 5%
  DLC: First Contact.
  Remark: Really hard to find such a pre ftl primitive. Waiting for the event to fire is also painful.
  
  
• Toxiods Questing Knights.
  Say no to third quest The Visitor. Give tech option and no tech progress.
  DLC: Toxoids.
  Remark: I don't even own this DLC, so no comment.

Obviously none of above apply if you are gestalts.

validity

The facts were extracted from Stellaris 3.8.2, checksum 947b. You could always argue I'm super bad at remarking though.