On a Nano XL space and looks are definitely the tricky part. One option is running a small internal reactor in the back chamber if you have the room. Some of the mini reactors are compact enough that they’ll hide back there and you won’t see them at all from the front.
Another option I’ve seen people do is run a small external reactor in the cabinet and feed it off a manifold or a small pump. That keeps everything out of the display and still pretty clean looking.
Just make sure the reactor output is near the skimmer intake if possible since biopellets tend to produce extra bacteria that the skimmer will help pull out.
Also go slow with the pellets at first. A lot of people start with like half the recommended amount and increase later so nutrients don’t drop too fast.