Alicornutopia

This is Jean's and Zari's homeworld. It's set in the 22nd century, so about a hundred years before the Star Trek original series. It doesn't comply perfectly with the history as we know it, because of some combination of "AU alterations I was interested in" and "I just couldn't be bothered to track down all the details we were given in a dozen different sources." Mainly, it's supposed to be plausible that it could in a hundred years look basically like what we see onscreen in TOS. It also continues in the grand Star Trek tradition of Unsubtle Social Commentary.

Vulcans found Earth in the 1950s, but didn't make contact due to Prime Directive rules. Humans pulled off FTL travel around 2050, which means the Vulcans show up and say hi. At our time, no other intelligent aliens have been discovered. The Vulcans are governed by an all-Vulcan Council; Earth is governed by the Federation, which technically also has Vulcan in its jurisdiction and a few Vulcans in in the government but the Vulcans mostly just think this is cute and do their own thing. There's settlements, both Human and Vulcan, on a hundred or so planets.

A bunch of features of the standard Star Trek 'verse are in the process of coming about, but the transition is not going super-well. This includes but is not limited to:

• Genetic engineering is super-illegal, on the level of "crimes against humanity." There's no death penalty, but any scientists found performing or researching genetic engineering are going to have the book thrown at them otherwise. There's also a major social stigma against it, due to the Eugenics Wars in the late 20th century. Basically, the stereotype of a genetically engineered person is "murderous supersoldier who tries to take over the world." This, of course, doesn't keep there from being a black market in genetic engineering, since it can do all sorts of nice things, ranging from improved abilities to curing genetic conditions to producing Vulcan-Human hybrids. Genetically engineered people are not legally allowed to exist, and while they're not going to be summarily executed if the Federation finds out, it's not going to be happy times either. They're in a similar boat as illegal immigrants in the present-day US, except there's nowhere to deport them to. Legally, they can't own property, vote, hold most jobs, lack a bunch of rights, and if they continue existing in defiance of the law are going to wind up imprisoned. Practically, anyone who's genetically engineered carefully hides that fact.
• There's a general attempt to impress the Vulcans by getting rid of religion. It's not illegal or anything, that wouldn't fly, but there's laws in place to make it very inconvenient, and something of a social stigma. (Socially, having any kind of religious beliefs beyond a vague spirituality is the equivalent of being a young-earth creationist living in a commune today.) Teaching your kids about your religion as "this is the truth" rather than "this is one thing that some people believe, but here are the scientific facts that contradict it" is an easy child abuse charge, and since it's hard to prove that you taught your kids in exactly the permitted way, religious people more or less have to raise their kids non-religious or lose them to child services. There's no longer any of the legal religious exemptions that exist today: churches don't get tax breaks, you'd better take off that head covering for your ID picture, etc. Any place with a dress code (school, work, etc.) bans visible religious symbols. Ministers who step one foot out of line with their preaching get slammed with charges for hate speech or inciting a riot. Muslims who pray in public get cited for loitering. And so on and so forth.
• They're trying to do the moneyless society thing. It's not working so well. The current government ran on "we are in an age of superabundance," and that's more or less the popular sentiment, but there's a fair amount of pushback because the transition away from money is going So Terribly. They don't have any one system replacing it (in particular, Jean wasn't able to offer a money substitute to Bar when he showed up in Milliways.) It's a mess roughly on the scale of health insurance in today's US. Everyone is fine for basic goods because replicators, so there's no one starving in the streets, but buying anything more complicated than that (services, experiences, things inherently limited) is a major pain. Some things work by lotteries, some are first-come first-serve, some you have to apply for. There's a fair amount of bartering and owing of favors. A system of "credits" sprung up, which is technically not money for [complicated legal reasons], but mostly functions the same way. Unfortunately they're not in super-widespread use, and also [complicated legal stuff] means that sometimes you'll be trying to buy something and it turns out that you suddenly have no credits in your account, or aren't allowed to withdraw any, or you need to have a certificate saying that you're gainfully employed and there's three forms and a six-week turnaround to get one of those.
• There's also an attempt to have One World Culture. This is mostly a social rather than legal thing. Having any kind of patriotic sentiments about your birthplace is considered creepy and kind of racist. Everyone speaks English; everyone but very old people speaks English as a first language; and anyone under 50 or so has more or less the same accent. Preferring foods or literature or clothing from one particular place consistently is, again, creepy and racist.

Now, not everyone is in favor of this stuff. Jean and Zari are members of what they refer to as the Resistance, which is an underground political group that works against all these things. The underground-ness varies by member from "I'm kind of sympathetic to the Resistance, I've mentioned it to a couple of close friends but I sure don't bring it up in public" to "constant secret identities and general sneaking around." Jean and Zari are in the latter boat, as are a bunch of people who've been caught out as genetically engineered. It's not technically illegal just to be sympathetic to the Resistance, but being actively involved is the equivalent of being a member of a terrorist group today, everyone thinks you're terrible and if you get caught you're likely to get denied a whole lot of legal rights. They do stuff that ranges from "anonymously advocating for stuff" to "helping genetically engineered people get fake papers" to "actively sabotaging government operations." There's a couple of thousand more-or-less card-carrying Resistance members galaxy-wide, out of a population of tens of billions, and proportionately more at milder points along the scale.

Shortly before we meet Jean, a sequence of events have led to about three-quarters of the active Resistance ending up gathered on a small outer-rim planet. There's a settlement there with a few million people unconnected to the Resistance. The Federation is actually trying to withdraw that colony because they've done some more environmental research and discovered the planet isn't a great place for a settlement after all, but they haven't really pulled it off yet. The colonists have been instructed to withdraw and legally aren't supposed to still be there, but starship seats are exactly the kind of limited resource that's hard to obtain, and working-class outer-rim colonists are exactly the kind of people who have trouble obtaining them.

So the Federation figures out that most of the Resistance is camped out on this one planet, and decide to take it all out at one blow. They've developed the Genesis device much earlier than in canon, which is a device that more-or-less instantly terraforms a planet, incidentally wiping out all life that's already on the planet. So they give one warning, which isn't actually enough time to evacuate, and then shoot the device at the planet. Jean says in thread that this won't even make the evening news, and he's right. Officially, the Federation terraformed a planet and there were some tragic casualties in the form of squatters who refused to leave despite multiple warnings.

With the hour or so of warning, everyone on the planet realizes there's no chance of evacuation. Most people hug each other and cry. Jean, who has gotten Milliways doors in the past and knows about the time-pausing effect, starts frantically opening doors while watching the minutes count down, with the plan to grab his sister and run and then hopefully find a way to rescue people with resources to other worlds. Unfortunately, it takes him a long time to get a Milliways door, and when he does there's only 2.6 seconds remaining on the countdown. Without time to get Zari, he jumps in and slams the door, and starts camping out in Milliways looking for someone who can save a planet that quickly. Which is where we generally meet him.