My first choice it to vent out a nondescript location within reasonable distance, a gable end wall perhaps. I do try to avoid roof penetrations. If you do need to go through the roof they'll have to pull and replace a few shingles to get the proper overlap on the roof boot. But there is nothing wrong with going through a roof and often times it's the best place to vent. As to venting through the soffit... First, just terminating the end of the duct into the concealed soffit space is bad. Bad bad bad. Even if you have a perforated soffit. Second; 1) Some jusridictions prohibit the practice outright. 2) Some prohibit outright if there are soffit attic or roof vent openings in the soffit. 3) Some allow soffit venting, but not within 3' of an adjacent roof or attic soffit vent opening. 4) The soffit vent should not be within 3' of a window. The distance restrictions are to prevent the moist air from being pulled back into the house. So can it be done? In some place it's against code, in others it's allowed but with restrictions. If it is done, again, you don't want to dump the air into the soffit cavity, you want some sort of termination hood or grill in the soffit itself. Some installers just use a round grill type of cover. Others use a specific "soffit hood", Fantech has one called the UEV-4 ( I think?) that has the upside-down "T" flow and includes backflow dampers on each leg of the "T".

You don't want this moisture in your attic. Fix it by spanning the gap with flexible hose secured with hose clamps on each side. Should take you about 20 minutes, if that.

I thought about going straight up with it, but I don't have a lot of room due to the angle of the ceiling. Plus, I am going to be using a canopy style hood, so the chase would have to be rather large to be in proportion with the hood, and I'm not sure how that would look. I did think about placing cabinets on top and then a chase above that, but again I am probably too close to the rafters in the attic due to the slope of the ceiling. Consequently, out the wall and into the garage attic seems to be the simplest way to go. Plus, that gets the inline fan away from the house and makes everything more accessible. I don't mind enclosing the vent in drywall to bring it up to code. While the vent needs to be in a soffit, what about the inline blower? It seems like the blower should be left out in the open, with the remainder of the duct enclosed? That said, I can see what you are saying about direct penetrations from the garage into the house are not permitted due to fire concerns. However, would a solid duct running from the kitchen into the garage attic and out the roof fall within that logic? There are no breaks in such a duct run, since the only openings are at the hood itself and wall/roof cap. So as long as the penetration where the duct goes from kitchen to garage is sealed with fire caulking around the duct, how is there an issue? Again, I don't mind enclosing the duct run in a chase if need be, but it seems like overkill....

Fortunately the fan is pretty close to the wall (8' run maximum?). Wall vent is possible although we are a little concerned what it would look like (unexpected to see a wall vent?) Wall is also a concern as the ceiling is cathedral and the steam, etc. is going to want to naturally travel up (away from vent). It would be alcove shower (3x6') with fan outside of the alcove (if ceiling mounted). Alcove does not abut outside wall. I'm not sure about ducting bending the 90 degrees as the duct would puncture the end of roof framing and the top of wall framing (the horizontal pieces). The exterior wall is shorter than average 77" and I am suspecting part of the reason a soffit vent may no longer be allowed for us is the space is very tight, if that makes sense. Duct looks to be around 4" diameter and wall top and end of roof frame is 2x4 (not 6", 40+ year old house). i agree side venting is preferable to going out the roof and having to deal with snow and ice.