Here is one problem with using a rotary axis with grbl…each time a different size cylinder of wood is cut, the steps per mm must be adjusted to match that particular piece of wood, not a huge problem, but just adds a bit of time to a project. Once I get the new electronics installed, it won’t be an issue as true rotary axis support moves the axis by degrees and not linear movement.
Not a show stopper, just something to consider if anyone plans on going this route and staying with grbl.