With LightBurn 1.4.05 it seems that the extra steps of manually editing the .nc or rotating the image is no longer necessary. Here are the steps that I performed.
Use Laser Tools > Rotary Setup and set as follows, except for the Object Diameter which is based on the material you are engraving.
Place the image as you normally would. In this case I am just writing the word “TEST” with a solid fill.
You then can use User Origin as normal
The only frustrating thing is that LightBurn does not calculate themin_b(mm) and max_b(mm) parameters that Snapmaker expects for running boundary checks (note, even though the header says the units are in mm for the B axis, they are actually degrees). This means that when you do a boundary check with Snapmaker it will make a fully 360 degree rotation. If the boundary check on the B axis is important for your application, you can edit the .nc file by looking at the header:
;max_x(mm): 30.21
;max_y(mm): 9.64
;max_z(mm): 0
;min_x(mm): -0.21
;min_y(mm): 2.36
;min_z(mm): 0
;Header End
; LightBurn 1.4.05
; SnapMaker device profile, user origin
; Bounds: X-0.21 Y2.36 to X30.21 Y9.64
Then using the formula Angle_BAC = 360 * (max_x - min_x) / (pi * diameter)
Which for my example would be 360 * 30 / ( pi * 80 ) = 43 degrees. Since I used a bottom center origin I would set the min_x/max_x to zero and add the following min_b/max_b:
;max_x(mm): 0
;max_y(mm): 9.64
;max_z(mm): 0
;max_b(mm): 21.5
;min_x(mm): 0
;min_y(mm): 2.36
;min_z(mm): 0
;min_b(mm): -21.5
;Header End
; LightBurn 1.4.05
; SnapMaker device profile, user origin
; Bounds: X-0.21 Y2.36 to X30.21 Y9.64