Here's some things I've picked up that might be useful. For context, I've worked roughly ~35 jobs since I started working (illegally) at 13. This includes all kinds of work including manual labor, food service, construction, sales, and dev/tech work currently.

Great Managers are almost unconditionally great leaders. At the core that usually just means they are well liked by everyone and well respected by everyone that works with them. The litmus test on this is to ask yourself who you "go to" if you have a problem, who you think knows the most about the stuff you are all working on and/or who could help navigate though things the easiest even if they don't know about them.

Typically, they trust you to contribute without observation or correction. This doesn't mean that they don't believe in improving the people they work with, in fact they believe the opposite. If they are looking to improve their people or their team they will do it in a structured, safe, methodical way that will help get the best results possible.

Great Managers are crafters of a great environment. They use their people to make a place that is: inspiring, motivating, resourceful, thoughtful, caring, safe... etc- in other words, they let build an environment to help people do the best work that they possibly can.

Great Managers also know a manager's tool box, but they are also selective of when to use the tools. This can be things like one-to-one meetings, "team building", or Awards/rewards, etc. (on the positive side) ...or on the dark side hard CCs, "performance plans", the full gambit of power moves, creating environments where it sucks to be a bad employee, etc.

Another secret about a "great manager" ... they almost always have another great manager next to them too (even if it isn't in title). This is actually part of the reason that Y/C prefers co-founders. Having one person with ultimate authority over a group of people is a bad ida. Great Managers know this and keep someone around them with equal stature so that you have the opportunity to go to different people with different problems, AND so you can disagree constructively.

They are also humble. The are accountable to the customer, to the company mission, to their boss (who might be the customer), and to their people. When things start going bad they accept blame first, and when things are going well they give the credit to who it rightfully belongs to.

Additionally, They work harder than their people. Why? Because it is a privilege to serve the people that work WITH them. They respect the opportunity that they have in front of them.

Lastly, and this is a big one for me... they are willing to get their hands dirty. The work that needs to get done is owned by them as well. Many times, these managers were really good at the work they were doing and leveled up because someone above noticed that they might be good at teaching people to do that thing. In other words... a lot of times they wish they could be doing the work that their people are doing, not glad that they don't have to do that work anymore. This exists because they take pride in their work, and thats why they have no problem getting their hands dirty or learning things that might help YOU do your job better. For a GREAT manager, there is no crystal palace, there is shit to get done, and they don't care if its them or you that gets it done.