Snapmaker U1 is amazing

Definitely avoid Bambu, they have been very hostile towards open-source developers! And this is speaking as somebody who owns an A1 bought before the ecosystem lockdown shenanigans (my printer is now in LAN-only mode to allow continued use of OrcaSlicer).

The Elegoo Centarui Carbon seems to be an excellent option from everything I've heard online. They recently released the "Canvas" multi-material unit, which looks pretty interesting, but the reliability of it is undetermined. It works fine now, but there hasn't been enough time to see if it will last. Could be a thing to consider if you will be using the printer for anything important! I've also heard that Qidi's Q1 Pro is excellent, and their new Q2 is the successor to that with support for their "Qidi Box". It looks like a neat option too.

Although much better than Bambu, as they support stuff like OrcaSlicer and OctoPrint out of the box, they aren't the most open. In both cases, they used a custom version of Klipper that is not open. I do know that there is the "OpenCentauri" project that is working towards an open Klipper for the CC, but full support (esp. for the Canvas) is not there yet.

Ideally, if within your budget, the Prusa Core One will be the most open option you can get. Great customer service, best in class build quality, repairable, etc. It supports the MMU and, in the future, the INDX for a toolchanger!

I love my A1 and A1 mini! But don't buy a Bambu labs printer.

I recently got an Elegoo Centurion Carbon. You can get them direct from Elegoo as open box for $250 shipped. And they just released the AMS upgrade for that printer for only $50. Granted, the AMS upgrade doesn't ship until at least next month, so I can't attest to the quality of that. I have enjoyed my time with the printer though. My first printer, and it's been painless.

I think overall, it seems to be a pretty low price for multi-color, and pretty decent printing.

PS: there's also a small community that are releasing custom firmware that'll let you fully escape the grasp of the company in case they also do silly things.

It's not awful to consider the anycubic Kobra X, takes a rather unique way of handling multicolour.

I'm personally using a qidi q2 combo, as I wanted multi colour and the ability to print ASA well... And not spending over 1k AUD.

My wife preordered the new Flashforge printer (Creator 5). Still waiting for it to come in, but early reviews look interesting.

4 head tool changer design. It's a little over your budget, ($699 USD currently) and they don't seem very linux friendly, but it does seem to be compatible with orca slicer. Don't seem to be as bad as Bamboo though.

Downside is you have to wait for it to ship. They seem to have had some sort of shipping snafu and preorders have gotten delayed. Looks like we'll be getting ours sometime end of June. Not sure when regular orders will ship.

A couple of years ago, I had an Ender 5. Can't recommend it. Went through 3 main boards before I decided to start modding it. Never did get it truly reliable.

I've only had one exposure with a multi-head printer, and it was incredibly messy. No matter what settings I used, there ended up being drips from the unused nozzle.

My most recent printer is an Anycubic Kobra Max 3, and I'd take the wasted filament over the sloppy prints any day. It's a bed slinger, so maybe not what you had in mind, but they do make one with an enclosure.