For you introverts who are managers, how do you do it?
I don't. I thought being manager would be the obvious career progression and it came by itself, I was the most organized and outspoken developer, so they offered me the manager job. In every job from then, the bosses notice that I'm knowledgeable, passionate, respected by colleagues, not shy to make a point in meetings if it's about a topic I know and care about, and they see me as the obvious candidate for a leadership role. And every time I say "Thank you, your trust means a lot to me, but I have to decline, I love being a developer, but I hate being a manager".
Now, when I was naïve and thought managing developers was the same as developing, just with more decision making power, I did the same thing I do when I hit something new in terms of software: I read books. I visited courses. I watched videos. I know how to manage people. I learned how to manipulate people. I just hate doing it.
So your first step should be: learn how to do it. Whether you like it or not, you will always fail if you don't know how it's done. If you decide to not do part of your job, or not do it well on purpose, at least know what you are doing wrong. Who knows, you might actually enjoy it once you have the knowledge how to do it properly.
I don't need to do a particularly good job, just a passable one.
That is a quick way to an early grave, depression or all around misery. Nobody can wake up and be happy about a new day knowing they will do a shitty job on purpose. So why are so many people doing a shitty job? They don't know. Even those idiots you want to scream at, even they got up thinking that they will do a good job today. That is what we take from our jobs: satisfaction of having done something properly. Even if it's just imagined because the person did not know better.
What is the minimum required to be a manager?
You can get that from a $5.99 book on Amazon more eloquent and in more detail than I could provide here. And if you really only read single book (I recommend a lot more) then let it be Peopleware.
So let me challenge that question. Let me ask a different one. What is the minimum for you to lead a happy and healthy life? Is the extra money buying you so much happiness that it can compensate for 8h per day, 40h per week misery? Developer right now is a well paid job, that can afford you most of what you want. Think of what you cannot afford as a developer, but could as a manager. How many hours can you enjoy that? Is it worth 40h per week of anything but work you hate?
Lets assume you want children, and that is pretty costly. What would make them happier, a used car at their 18th birthday from a parent that was always grumpy, unhappy and unapproachable because of the job they hate, or a used bike from a fun and motivated parent who is always around and enjoys life?
Money can buy you a lot of things, but none of those things actually matter. Money is important up to the level where it ensures you can be healthy, well fed, have a nice home, but after that, more food or a nicer home won't do anything if you feel miserable about the large part of your life that is work.
So to sum it up: there is lots of knowledge out there on how to manage people. Read the books. Watch the videos (I guess. I'm old, manager instruction videos came on VHS when I tried, I never did that). Get a course on management, I'm sure your employer is happy to pay to see you trying your best at your new job.
But if you find out that everything you learn is just "knowledge" and you still don't enjoy that job, don't be afraid to say that. Don't be afraid to step down and enjoy your life in a job you really like. Being a "boss" does not make your life happier, money can not buy you happiness. If you like it, great, but if you don't, don't get hung up on it.