You need a Raspberry Pi!
Or maybe 5, or 8 or more of them…. there is no such thing as ‘too many’ so purchase away. Raspberry Pi 4 is the latest main project board, but there also exists smaller, less powerful boards such as the Pi Zero, and Pico boards.
Raspberry Pi’s are small deck-of-cards sized devices that are essentially small single board computers, up to 8GB of RAM for newest models. These make an excellent base for a wide range of products, think security camera systems, robots, media servers for playing movies and content, NAS (Network attached Storage) or many many other uses. Routers, Ad-Blockers, the list goes on. Bottom line, you need lots of them! They can be used as regular computers for checking email, or for many other purposes, these are extremely common with many sectors of use.
Plug in a keyboard, mouse and screen using micro HDMI ports, and you have a basic computer! Raspbian is the default Operating System for these, but you can install just about any type of Linux on these that you wish. MotionEyesOS is a good one for developing your own home security camera system using Raspberry Pi’s, and there are many other OS’s that you can choose to run. Kodi is a popular OS to use for streaming media, you’ll find many a RP4 attached to the back of people’s TV’s serving them up their entertainment using Kodi on a Raspberry Pi. You’ll need a Raspberry Pi computer, a micro SD card and a power supply to get going.
To burn an Operating System onto a micro SD card to use in your Raspberry Pi single board computer, use Raspberry Pi Imager program:
https://www.raspberrypi.com/news/raspberry-pi-imager-imaging-utility/
Where do I get them?
Lots of great sellers have them available, however they are a little hard to come by right now. While they used to be about $55, they now claim a much higher cost, so check around often for new RP4’s to come out, or newer models:
https://www.makeuseof.com/where-can-you-buy-raspberry-pi/
eBay, Amazon, etc
Above is a typical Raspberry Pi 4 board, below are other Pi boards
Above is the Pi Zero 2 Wireless
Above is the Pico development board