Prusa is top of the line for open source and very much falls into “works out of the box”. The other bed-slinger style printers like Ender are cheap but tend to have issues and are a money-sink for upgrades to get them working (lots of mods there). If you’re into hacking and modding stuff though, look into Voron printers. I’m not sure if any of the Voron versions fall into your budget, but you can buy a kit or do open-source. They’re self-built, extremely fast, customizable, and really meant for the people in the printing community who like to program and mod things.
Prusa is top of the line for open source and very much falls into “works out of the box”. The other bed-slinger style printers like Ender are cheap but tend to have issues and are a money-sink for upgrades to get them working (lots of mods there). If you’re into hacking and modding stuff though, look into Voron printers. I’m not sure if any of the Voron versions fall into your budget, but you can buy a kit or do open-source. They’re self-built, extremely fast, customizable, and really meant for the people in the printing community who like to program and mod things.