I have the same question. Did you ever get an answer or did you end up plumbing it outside? If so, how are things working?

Mine drains to the outside.....into a planter actually.

revisiting this...to avoid breaking slab to install a drain line. Did anyone else drain their combi through a wall to a planter box or yard area?

Drain line from steam oven would be mostly warm water. There may be a bit of food scrap in small pieces. I often see bread crumbs when I run rinsing program on the oven floor. Generally these shouldn't be any harmful for plant.

The oven requires descaling every now and then. And that's probably your main consideration where it should drain to.

Another point, is that if there is no odor trap, would there be any crawlies trying to get into your oven?

good question. Probably so....since I'm in Hawaii I can now visualize B-52s (our giant flying cockroaches) and centipedes inviting themselves in! Eeek!