Before you go on a multiple-year trip accessible only by hyperspace relay, you download every out-of-copyright-work of art, literature or science your civilization has ever produced and stick it on your ship's computer. You do this even if you are, frankly, kind of dumb; it is just the obvious thing to do. You are not going to think of everything you need, and no matter HOW confident you are that five-dimensional math is beyond you or that you have no interest in the works of Falazon-2114, some conceivable emergency might mean that you need to repair a damaged hyperdrive or persuade a colony founded on his works that they desperately need to join the League, and when it is essentially costless to take everything, that is what you do.
This, at any rate, is common knowledge known even to the pilot of the Finite But Extremely Large Bounty, whose true name is a thirty-six digit hexadecimal string and whose usename incorporates sounds found not only not in English, but not in any language spoken by dogs, chimpanzees, mosquitoes, or any other entity that does not prefer to communicate exclusively via signal broadcast. We can call him Nau, or Fodion, or GODDAMN IT, since these are all noises he is going to make very, very soon.
Not that any emergency has hit. No, he's had a peaceful trip; no need to exercise self-control, no need to make decisions calling for twice his intelligence, just regular drop-offs of signal beacons to mark his progress and slightly less regular placement of mining replicators on the occasional unusually valuable asteroid; when the pickup ship comes in his wake, it will find the asteroids neatly sorted into their component materials, all carefully packaged and floating by the beacons for immediate delivery to the nearest orbital factory. He's been being choosier than most miners would, with his beacons, but the whole point of taking a job mining asteroids is so you can generate positive value for the world without ever having to interact with any part of it that is not best primarily understood with reference to Newtonian motion, and the longer his trip, the more he can stay in his cabin, reading books written when the League's average IQ was three standard deviations lower than it is today and even mostly following them.
And as long as no emergency hits, that's exactly what he's going to be able to keep doing. He sets his hyperdrive going and -
"You think you have an internet" is a mutter both low and outside the human auditory range, given when he sees what it looks like. (Whether it is outside the Amentan auditory range is unknown.)
He is absolutely confident that if their machine translation has caught up to his language, his can catch up to theirs. Has it yet?
... Okay this is super embarrassing and he's going to blame the fact that his ship-computer was busy running a diagnostic instead of devoting most of its attention to this.
"My machine translation will be slightly slow." Pause. "Your languages appear to have no connection to any Earthly language, which is what they were trained on. It may take some more minutes."
"Do most all through the galaxy tend to resemble a particular kind?" asks the green. "That's very surprising!"
"... You are not descended from colonists ultimately from [Terra/Earth/Sol III]*?" Well, that's what the computer initially thought, but the computer is so obviously wrong! They have hair on their heads and everything!
(*: Including lots of synonyms just in case they forgot one old name!)
"We are confident we evolved here! We could be wrong but we have a fossil record and resemble other animals here."
"That is the most bizarre thing I've heard." If they and the computer agree, he's probably wrong! "You greatly resemble the juvenile form of my species."
Okay, there we go! He's got onto their so-called-internet. He'll start some scans now and check the results later when he's not talking to someone.
"You can find pictures of juvenile Amentans on the internet if you wish!" (He can. It would be hard not to, without dedicated software add-ons to protect one from an assault of baby pictures from all directions, which he can also find.)
... Okay, why do these people like baby pictures so much. "We also pass through a stage like that, even earlier in our development."
"That's interesting! We don't look like you later on." There are indeed pictures of old Amentans; they get wrinkly.
"We used to do that. We fixed it. We can fix it for you if you want."
For values of 'we' that include 'his entire civilization' and does not include 'one shipwrecked miner.'
"That's amazing! We look forward to it. What other technology do you have that we don't yet?"
He checks his pocket everything. "... Apparently, nine-tenths of my materials list." He pauses. "We can make metal serve as substitutes for flesh. We can make you continue to be alive after your body dies, though that is difficult. We can produce all sorts of things very efficiently." He pauses again. "Obviously, we can travel between star systems at practical speeds."
They'd be stupid not to be.
"We share our technology with underdeveloped civilizations." He pauses. "Unfortunately, I am not a hyperspace engineer. If I could get my ship back home, I expect I could find you one." Another pause. "Or two. Or six. Or thirty." 'Manpower' is not the key resource, for the war effort, but it's still valuable. And they'll be more valuable, after they've been industrialized.
"Yes! We will do our very best to help you and get in contact with your home civilization!"
YES! These are the NICEST ALIENS!
Next step: Reading their internet to determine if they actually are the NICEST ALIENS or if this is just some kind of fraud.
The internet is, apparently, very sincerely excited about the prospect of helping the crashed alien get home to his own civilization which has FTL! This is clearly the best thing that has ever happened to the nicest aliens and they all want to support this project in any way they can! People are talking about how to track-switch into any of the fields it looks like he'll need and posting aliensonas of themselves moved more in his direction cosmetically captioned 'me at age 72'!
The nicest aliens are ADORABLE.
They also seem to have a thing about hair color! He has no idea what the thing is, but his computer says that the word they use for 'grey' also means 'soldier', or something? It seems to be a very close synonym! What's up with that?
"Grey" means the color (all hueless shades lighter than black, including white) and is used as metonymy for the caste, which in most languages also has one or more terms of its own that aren't metonymy and which, depending on the language, may have as etymology "soldier" or "warrior" or "guard" or "runner" or "strength" or "embodied" or "dance".
A caste is a category of Amentans specialized, through training and hereditary selection, in a category of occupations! Greys do soldiering, policing, and athletics, and also some kinds of gambling, sex work in many countries, dance, and a few cornery occupations shoved in for historical reasons.
Huh! He's somewhat curious what the other castes are! He wonders if it's anything like how his people divide things up, though that's more commonly based on life stage and interests.
There are blues, who do rent-collection on land ownership (looks like others can own land, but collecting rent on it is out of caste income) and governance and judiciary. There are greens, who do academics and the arts. There are yellows, who do clerical and administrative work of all kinds. There are oranges, who do healthcare, childcare, eldercare, social work, sex work wherever it isn't grey, and childhood education. There are purples, who do everything else, including but not limited to farming, shipping, construction, engineering, manufacturing, cleaning, and the service industry.
Okay so his entire planet is purple.
... That's not fair. There's some greys and babysitters and there's some people who design fiction, which would be green. And he... guesses he could fit some people into yellow??? Mostly they automate that. And he supposes that what the League leadership has instead of blues and research-greens might still count as people, but he's honestly a little iffy about it; by the time you get up to that intelligence level you're not... really his kind of person? You're a different kind of person?
... Speaking of which, where's all the smart people on Amenta? There's got to be someone smarter than he is, right? He's really dumb, but a lot of the internet conversations seem to be even dumber. Maybe they just use a different internet?
Most Amentans are also purple. They seem to be actively subsidizing more green than they strictly need, hoping for a big break - like "an alien crash-landed and we have to invent 200 things to get his ship working", so they feel pretty smug about this decision right now.
Internet conversations are in fact often dumb, though some of them might be humor or performance art masquerading as dumbness. If he goes to more filtered green-field fora like Project Quicksort or something, that's where Amenta's best and brightest who are not literally at this moment trying to invent 200 things are hanging out.