I printed my LR3 core on my stock Ender 3 Pro. Took like 18 hours, but it came out just fine first try
Edit…
Well, not completely stock… it was converted to use Klipper, so I was able to do Skew compensation.
I spent some time checking frame square, getting it as good as I could, then ran Calilantern and adjusted skew.
But was still using the stock Bowden extruder and all that