[cityofdelusion]

You are sadly getting a lot of answers completely ignoring your requirements.

A Voron or RatRig are right up your alley. They are highly customizable, buy a kit as a base, then upgrade components as needed to do more complex printing. They are completely open source and repairable with no phoning home or any other shenanigans, the GNU/Linux of 3d printers. If you have CAD and machining experience it should be fairly straight forward.

My Vorons are both extremely reliable, I just hit print for 99% of my stuff and it just works with either auto leveling or static fixed offsets (depends on the Voron chosen). If something doesn’t work out, there is an enormous community with many swappable components and the machines are upgradable year after year, or can be kept in a specific older configuration.

[abhorrence]

As someone who owns both a couple Vorons and a couple of Bambu's printers, I do think for a lot of people the difference between the two can be "3d printers are my hobby" vs "3d printers are a tool". It's not that Vorons can't be reliable, in fact a lot of the reason why say the X1C is so reliable is because its design essentially started life as a Voron. But because you have to assemble them, they just aren't as "plug and play".

[fooqux]

Sure, but go and read the OP's requirements again and tell me if you think they care about needing to assemble them.