It's an issue with how typescript is compiling the package, so instead of the intended new Booru('sb'), you need to use new Booru.default('sb')

I will see how I can force typescript to not do that (or expose a Booru.for('sb')), meanwhile you can use Booru.search('sb', tags)

great, but now i get this (unrelated to bot code)

const Booru = require('booru'); // load the fucking uhh
const sb = new Booru.default("sb");
const Discord = require('discord.js'); // make discord actually need discord.js
const client = new Discord.Client(); // make bot do a fucking exist
const prefix = "#"; // prefix what the fuck else to say
const version = "3.1 alpha";
const botname = "MSPABot";
const hostsys = "Debian 10 using Windows 10 Home";
const imgsfw = sb.search(['homestuck'], {limit: 1});

client.on("message", (message) => {
// Exit and stop if it's not there
if (!message.content.startsWith(prefix)) return;

if (message.content.startsWith(prefix + "imgtest")) {
message.channel.send(botname + " " + version + " " + hostsys + "\n" + imgsfw[0].postView);
}
});

client.login("NO TOKEN HERE EHEHEH");

gives:
TypeError: cannot read property "postView" of undefined
should i put this in a separate issue?

It's a separate issue, imgsfw is a Promise so you need to either await (inside an async function) or use .then()

booru@2.1.0 now exposes booru.fromSite(site), since Typescript doesn't really have a good way to get around booru.default that isn't just not using export altogether.

Let me know if that works for you