Well, the question still remains of “symbiotizing what”? Fungi on earth range from saprophages, which decompose dead matter into nutrients, to mycorrhizae, which form symbiotic relationships with plants which produce nutrients. In either case, they’re feeding off of things, it’s just the source that varies. All living things need to gain energy somehow.

The mycelial network is spooky and probably feeds off something more abstract, since sci-fi and all that. That said, maybe it’s in some sort of symbiotic relationship with the multiverse itself? There’s so much energy in a galaxy, let alone a multiverse worth of galaxies, that it’s not hard to imagine a fungal network feeding off just a tiny fraction of that energy. And interstellar space has relatively low energy, so it makes sense the network wouldn’t build hyphae there.

You’re right that they never said it only works in the Milky Way, I had just assumed that since it peters out at the border of the galaxy that it ends there. And if it resumes in another galaxy, it seems like it would be discontinuous and thus a separate organism. But I suppose if you imagine it as a wholly separate subspace realm, with hyphae that connect out wherever there is sufficient “energy” of whatever sort it feeds off of, it makes sense. And jumping to another galaxy could be a cool twist indeed!

I would give anything to be an astromycologist

Ok guy who says something exists everywhere and isn’t omnipresent, and that there’s no superpowers except for the one guy with superpowers

Proteins that could not be adequately replicated by a computer

Yeah, but that requires a strange alternate future where computers are simultaneously both faster than today’s computers and also not any faster.

And yes the simulation needs a compatible physical interface.

I’ll help out. Here you go: https://www.askamathematician.com/2012/07/q-how-does-instantaneous-communication-violate-causality/

I love it when sci-fi teaches us about real stuff. The problem is that when you mix instant and classical (non-instant) communication channels, you get situations where information time-travels, and the receiver gets information from the future. This breaks causality (present based on future events), and so nature rightfully abhors it.

The closest we’ve come to instant communication is the use of entangled particles, but we can’t make practical use of the phenomenon. Touch one such particle, and it’s pair instantly changes to the opposite state. The catch is that you can’t know when to observe the particle, nor can you know what the original state was, via the same mechanism. So you still need to use normal photons moving at slow-ass light-speed to communicate that meta-information, thereby undoing any attempt to exploit it.

Ah… ok, wow, that’s a lot of relativity to explain from scratch for a non-physicist. There must be someone else…

Here, this one is a bit dense but it addresses Star Trek by name, so:
https://www.youtube.com/watch?v=mTf4eqdQXpA

Bonus points for starting with the point that forget warp, subspace communication breaks causality already, so you don’t even need to boldly go anywhere for any of it to be kinda busted.

If that’s a bit too dry you can search for a similar subject line, there are TONS of explanations like this one out there.

Anyway, none of it makes sense, it’s all for funsies anyway. Suspend disbelief, ye nerds, and enjoy your sci-fi.