These are just links to hardware I frequently use, and wrote my own documentation for:

Printer Controllers

• Duet 3 Mini 5+ (2023: EUR 150-200), 1x in use and very satisfied with it
• MKS Monster8 (2022: EUR 50), 2x in use
• Mellow Fly Super8 V1.2 (2022: EUR 80), Duet clone running RRF, 1x in use

Single Board Computer (SBC)

• Orange Pi Zero: I use a couple of them as Print3r/Prynt3r printhub: I connect multiple USB-based printers, and used Print3r/Prynt3r network-based remote printing capabilities

Embedded Single Board Computer (eSBC)

• Milk-V Duo (EUR 5.00-9.50) Ethernet over USB, Linux, Python

Microcontrollers

• ESP8266 (EUR 2.50-3.00), Wifi, Lua, MicroPython
• ESP32 (EUR 3.50-5.00), Wifi, RTOS, Lua, MicroPython
• Wemos S2-Mini / ESP32-S2 (EUR 3.00), Wifi, RTOS, MicroPython