Extra galactic, diminsional, spoons Ai's..
Good reason for the galactic barrier!
Except it didn't seem to be stopping them in Picards season finale...
Wasn't The Doomsday Machine also extra-galactic?
Yes, but not extra-dimensional (and, as the novel Vendetta points out, was barely extra-galactic, as there was no way a weapon that feeds off planets would be able to get here, still powered up, from very far outside the galaxy).
What they had in common was an utterly un-humanlike physiology. One is almost tempted to think that each galaxy at this day and age is under the control of a single superspecies that only allows its own kind to flourish there, and the Milky Way has humanoid overlords (that is, they used to be humanoid and are still fond of that shape) while Andromeda is controlled by somebody who used to look more or less Kelvan (that is, with a hundred tentacles).
I hardly think it's a universal law; the Milky Way just happened to have the Progenitors that nudged evolution on many worlds, the Preservers who transplanted humans, the Skagarans who transported human slaves, who ever kidnapped Amelia Earhart...
I wonder if there will be any repercussions from Soji being cool with pointing extinction at all organic life for a good while there. She doesn't have mind control or Data's emotion chip to fall back on, it was a real decision to nearly wipe out everyone she met during the series
Remember how cute she and Kestra were together? Yeah, she nearly murdered her...
Maybe this is why the Galactic barrier exists? To protect the galaxy from the AI "Federation" Maybe why there was a "Presevers" in the past because maybe in the past at some point, the AI federation came into our galaxy, and we fought them off, and set up the barrier, and the perservers went to work to reseed life around the galaxy??
Just a thought.. The Barrier is just one of those things that is sitting there waiting for a good story.
May I suggest the Q Continuum novels and the third Return of Kirk trilogy of novels?