I second (nth) the other comments regarding getting a Chinese CNC3040 (or similar) "engraving" machine.
They're widely used in the ornamental wood / stone engraving industry afaict, and have a decent amount of refinement by now, they're machines that work. I recently started making simple molds / enclosures etc cut from aluminium on a CNC 6040 class machine and it performs well for that task (cutting depth around 0.5 - 1mm keeps it happy depending on size of milling bit).
In the makerspace I'm in I set it up with control from an Arduino Due running TinyG G2 firmware. They are normally designed to be operated from a PC running Mach3 software.
We got the 2.2kW spindle since it was a small cost increase from the 800W one (the smallest one needing an inverter). I think 2.2kW is overkill in the end but 300W might be a bit puny for aluminium.
If you really want a toy like the Sienci Mill One, I recently bought a toy engraving machine from a seller on Taobao which is a much more sound implementation of that concept of barebones machine:
https://item.taobao.com/item.htm?spm=a1z09.2.0.0.xBweLa&id=531855133304&_u=dk1rlm9cff9Price is around 700RMB (but shipping to Canada would add a lot of course, probably more than the price of the kit). Amazing price given that's for the full kit including power supply, spindle, and custom Arduino-based control board!
It works amazingly well for milling PCBs actually... I got very good results down to 0.5mm QFN by using Z-axis mapping using a contact probe. It's a much more sensibly designed kit than the Sienci one though, aluminium extrusion frame and dual guide rails with linear bearings on each axis. And what's not aluminium is some kind of milled engineering plastic.