I recommend that you use a Raspberry Pi 4B - especially if you are just starting out. They’re very easy to get right now and the prices are getting down to where they need to be. You’ll see people using a variety of “hosts” (including other versions of the Raspberry Pi, Raspberry Pi clones, old laptops they’ve loaded Linux on, etc.) instead of the Raspberry Pi 4B but when you’re starting out, I HIGHLY recommend that you don’t do that - you’re just going to add to your workload and you won’t be able to get very specific help when things don’t work.
At the risk of annoying this forum’s hosts, do NOT buy a packaged Klipper solution like the Creality Sonic Pad or a BTT Pad7. These products state that they provide an easy path to working Klipper but they’re basically lying. The problem is they don’t use standard versions of Klipper so while they will work in some instances if you have problems you’re all on your own - the Klipper team will not answer questions and the manufacturers do not provide any kind of acceptable support. 3D Printing Canada does have experience with helping people set up Sonic Pads but they charge for the service.
If you’re just starting out with Raspberry Pis but reasonably technical, I’d recommend something like a basic board:
when I say “reasonably technical”, I’m presuming that you have a few spare parts (USB Keyboard & Mouse, 2A USB power supply and SD Card) lying around and can source what you need, otherwise, you might want to look at one of the “Starter Kits” in the link above. Personally, I think the starter kits are overly expensive for what you get but they’re not terrible starting places if you’re new to Raspberry Pis. There is a ton of excellent online resources for getting a Raspberry Pi working and becoming familiar with it.
I should point that that if you’re going to run Klipper, you’ll need at least a 64GB Micro SD Card. You’ll notice the starter kits have 32GB SD Cards and they’re generally floor sweepings. Buy a name brand (ie Sandisk or Lexar) SD Card from Staples as that should avoid any SD Card issues.
As a final Raspberry Pi requirement, you’re going to need to have a network connection (Ethernet or Wifi) for downloading application code via SSH as well as interfacing to the printer (more on that below). Again, there are excellent online resources to show you how to get things running.
Looking around, I can’t find what I would consider a great (or even good) introduction to Klipper, especially for people who are working with their own printers.
The best way to get Klipper going is to use an app called “KIAUH” which will install Klipper and other utilities for you:
Just looking at the page, I see that there is a brief introduction on how to set up your Raspberry Pi for KIAUH - it’s in no way a special set up but the few words are useful.
Using KIAUH you’re going to install Klipper followed by “Moonraker”. The Klipper application is the interface between the gcode running on the host (Raspberry Pi) and the printer’s main controller board. This means that gcode does not get loaded into the printer’s main controller board but is processed by Klipper in the host and sent as execution commands to the main controller board.
“Moonraker” is the Klipper interface to the front end interface and the front end interface can be a variety of different applications with “Mainsail” being the most popular one. “OctoPrint” is a front end commonly used with Marlin firmware but Mainsail is a) better and b) very will supported and provides you with a nice web interface so you don’t have to worry about an LCD on your printer or having to deal with SD Cards with gcode - you can drag and drop gcode files from the slicer directly into Mainsail and print from there.
Once you have Klipper, Moonraker and Mainsail up and running, you’ll have to Flash your main controller board with the Klipper firmware and set up your connection to your Raspberry Pi host. I highly recommend using a USB interface - for some reason people prefer a serial connection, but that means a custom cable and a lot more fiddling than with USB. USB is more than fast enough for Klipper and easier to set up and is generally more reliable.
I would suggest that you now do a search on “Klipper Introduction” and read a few web sites and watch a few videos. Along with this, when you start working with it, keep to a minimum, just Klipper, Moonraker and Mainsail - you can add displays, cameras, accelerometers and other things later when you’re comfortable.
Sorry for the long winded answer but hopefully I’ve answered some questions and not scared you off.
Personally, I find Klipper to be a lot less clunky and kludgy than Marlin and having everything web based is a real positive.