stands, recorders, and cables and hubs!
I'll start with cables - how to get all the bits you've assembled connected. If you have a laptop or a tablet, you'll likely need to have an extension hub to get everything plugged in if you've gone for any of the additional equipment listed in the previous 2 articles. Modern laptops and tablets tend to have only one USB port or none at all, and in many cases you'll find only a type C (or lightning connection if it is an IOS)
You many need a headphone jack, or two USB ports and you only have one, or you need an HDMI connection for your second screen and you don't have one.
The answer is a "hub" or an extension to your computer. This is a small device that plugs into a port, and multiplies it. Magic.
If you need three USB ports and you only have one, you can buy a hub to plug into the USB that has room on it to plug in two or four or more USB cables. Something to watch out for: make sure they are USB 3, not USB 2. They'll be coloured blue on the inside if they are USB 3. You want this because they are much faster the USB 2 which means less lag between devices.
They come in two versions - ones that get their power from the computer to which it is plugged, and ones that need to be plugged into a regular AC plug-in (a powered hub) There are limits to the amount of power that a computer powered version can put out, so if you are setting up a semi-permanent studio and can plug in, it is better to get that kind. Depending on what you are plugging in to it - mics, webcams, monitors, you may only be able to run 2 or 3 things without that external pwoer. But if you have two periferals only and you need to move your gear around, go for one powered by the computer.
These are also called "docks" especially ones that plug into your USB type C port and give you a bunch of other options.
You'll also need cables to connect the peripherals to the hub or dock. Get good ones - USB 3, not 2. Gold end connectors for HDMI is often an indication of upgrade. worth it.
Name names, I hear you say. I had a bunch of cheaper things kicking around from old projects but have now two from Anker, and I'm really impressed. They are small, mostly metal not plastic, they have beautiful smooth connectors, and they work. One is a 5-in-1 USB C Ethernet hub. It goes into the C port on the computer and has a connection for an ethernet cable if I don't want to use wi-fi as well as an HDMI cable and 3 USB 3 ports. The other is a plug in power version that has USB connectors which I use for my cameras, and also to charge my tablet.
And so many cables. Braided cables from whomever are nicer...
You may be happy with the "tech look" of many cables strewn across your floor, but cable management is a thing. I have some rolls of velcro made just for that purpose - they have the hooks on one side of the tape and the gripper on the other side so you can cut a strip and wrap around and voila! This is a big improvement on the green masking tape I was using... You can also use this to secure your bundle of cables to the leg of the desk, or the stand, or to bury under a carpet.
Stands - you'll need a music stand, obviously, and a stand or something to put an external camera on if you're using one. You can get cool ones with feet that roll around, or microphone boom ones, or clamp-on, or whatever. Hard to recommend, as every set up will need something different. I'm currently using a roll around stand with a goose neck that I bought to hold a tablet in position when I was still using a tablet for lessons. It is a bit of overkill for a tiny camera, but still handy because I can move it so easily without getting up from my chair. If you are using a tablet, it would be worth it.
Recorders - I used to use a Zoom video recorder for some classes (not related to the Zoom on-line company). That or a DSLR or point and shoot camera could also be used as a second camera if they have HDMI connection.
You may be able to record the lessons at the same time, so you can play it back later if you are a student, or share it if you are a teacher. But videos take a lot of storage space, so you have to consider that. You can also record your lessons on Zoom, or allow others to do so. I've always encouraged students to record their lessons for study and practice, so this was a no-brainer for me. However the subject is complicated worth another whole article. Ask me if you want to know more and I"ll write it up!
A curtain/backdrop. Depending on what you're teaching it may be advantageous to have a curtain behind you. I've had one over the shelves and door in my studio for many years for this purpose, and it's practically the only thing that hasn't changed. It's perfect, and easy to tie back when I need the door. For the purposes of the camera, a dark colour is helpful to show the detail in the foreground. For the same reason, it is better to not position yourself in front of a window, unless you have a dark curtain on it to eliminate the halo effect. Even a small portable one can improve things - one of my students uses a piece of cloth over something (don't know what) just behind her harp - makes it easy on the teacher. Pianos provide their own backdrop, and other instruments may or may not need something.
That's it for now, but I'm happy to write more if you have questions - just ask in the comments.