Another option on the Raspberry Pi front are the CM4 compute modules. The BTT Manta controller has a CM4 socket. CM4 boards are a bit easier to come by than regular Pi4 boards, and the combination is more compact as the CM4 sits on the Manta board. The CM4 has onboard memory that is better than the SD card so an SD card is not required. The Manta is basically the Octopus reworked to take the CM4. If I didn't already have the Octopus and Pi4 I would use a Manta and CM4, and I may change to it yet. If a CM4 is not available BTT makes a replacement for it (CB1) that is equivalent to a Pi3, and one could always start with that. I was able to get some CM4 boards, they are not off the shelf but when in stock they take much longer to sell out and quantities are not as limited as regular Pi's so you can get several. The CM4 boards are available in many different combinations of memory, eMMC and wifi/no wifi from $25 to $95 retail. For Klipper 1-2 GB ram with 8-16GB eMMC and Wifi is about right and the regular pricing is around $40-50. The CM4 boards can be used on various carriers to essentially be regular Pi4's, or optimized for specific applications.