the dwarf galaxies that orbit the milky way are much closer than andromeda. Yet, they too are too far away for any tech described in the game to reach.
What's between galaxies tends to be filaments of hydrogen plasma ....still very sparse...but not a true vacuum.
en.wikipedia.org
The way we transit hyperspace in elite seems to vary depending on the engine/fuel tech used. The current method is frame shifting ..which is a nearly instant traversal of hyperspace to the destination. However, unless fdev does more retconning or already has...there has been tech in the past that allowed navigating hyperspace ....where travel in it took significantly longer and required hyperspace beacons and such. one could imagine some kind of generational hyperspace journey if something could navigate hyperspace without any kind of beacons / satellites to correct your course ...since there wont be stars or anything for huge distances (in 3d space).
Also, one could imagine some way to travel hyperspace to reach vast distances in normal space without going very far in hyperspace at all.. since we only perceive travel in 3 dimensions and tunnel thru hyperspace's higher dimensions to reach a destination in 3d space, there is no reason to believe there isn't a path that we could take to appear anywhere in the 3d universe going any arbitrary distance in this tunnel. Perhaps it just takes more energy to establish the pathway. Perhaps the route is just far more complex. Perhaps hyperspace beings live in the voids between galaxies (well ...whatever cross-section that would be in hyperspace) and they prohibit anyone from traveling between them in self defense.
edit: current FSD's adopt the "energy" option. where making a tunnel thru hyperspace to traverse out to a destination in normal space always requires an amount of energy that scales with the distance the two points are in normal space. So we are limited in how far that tunnel can be made by the total amount of energy we can process when opening the tunnel (for a given drive efficiency). So your only option is to increase the efficiency or increase the available energy from the fuel - to increase the range. The obvious max limit here is total annihilation (e=mc^2). So if we wanted to do the math and had actual numbers for efficiency of a given fsd in the game ...and available energy of the given fuel we use, we could figure out the theoretical max energy if the fsd was 100% efficient and the fuel was 100% available and get a max distance any fsd tunnel could ever be given some max single burn quantity. It would likely be far less than infinite at least, and anything less than 100% efficient would probably produce more heat than any ship could absorb without melting once the attempt got over a certain energy amount.
eg. if your FSD was 99% efficient. That means 1% gets turned into heat. Lets assume 50% energy available from 8 tons of fuel. that equals
359502071494727 MJ of energy available and 3595020714947.27 MJ as heat. That's something like 3.5 Million Tera Joules of heat. That would be like your ship absorbing over 55,000 hiroshima atomic bomb's worth of heat at once.
So i think it's safe to say that over a certain energy level, we no longer can traverse hyperspace the same way as our current in-game ships.
And in fact, it seems like the FSD drives themselves, must be a couple orders of magnitude more efficient than 99% as we routinely consume up to 8 tons of fuel ...to the point where it is nearly 100% efficient already so that waste heat is easily absorbed in most ships. It stands to reason then that the variation we see in the game is due to fuel energy availability and that the fuel isn't all converted into energy but rather somehow used in the process of jumping in other ways. explaining the constant fuel consumption but varying drive size and distance output. We're talking probably only 0.0000000000001% of the energy used gets converted into waste heat.
