If you happen to have some uncommon hub in a non-standard size, then maybe a hub adapter will be more trouble than it's worth. But it's more likely that you can have one that's a-okay. Just be sure to order the right size.
Just started skimming through the thread and saw this, relates to my build somewhat.
I am a first time builder who purchased a goofy bike to motorize. there's a thread for it if you want to tell me what I'm doing wrong (please do, thats why I'm posting pictures)
During my time researching for this build (and lurking here) I learned a lot of pros and cons for for different ways of attaching the drive sprocket. and as far as I can tell the best methods bar none is a custom wheel hub built for a sprocket on both sides (you know, if you have sever thousand dollars or a high tech machine shop.
I had maybe 150 dollars I could spend on this above the cost of the kit itself and the bike. and for my bike specifically there was a short list of undeniable facts: replacing the rear wheel is expensive because it's an oddball size, even people skilled in this craft had troubles mounting rag-joints on this bike, and for being rare and expensive to replace the rear wheel is not super-high quality.
Watching youtube videos about this I decided to myself that aligning a rag-joint on this frame had the potential to be a massive hassle. it's obviously a skill that one develops over time and I set my learning curve too high.
not to mention the thin, steeply angled spokes. or the overly wide but not particularly thick hub.
I started to get worried when I saw one hub adapter kit that was built only for this bike that involved drilling nine holes through the hub.
Then I saw a clam-shell adapter.
Then I bought a caliper to measure my axle.
Then I bought a clam-shell adapter.
I am not trying to say that my build needed the thing to work.
I'm saying I needed the thing to work my build.
As a first timer, knowing that my drive sprocket was just way overbuilt and basically impossible to mess up installing, gave me a good backing of confidence for the whole project. the thing was pretty expensive, but it is a precision machine part built to exact specification for that size axle.
(Sorry about this giant post. Tried to drop in two cents, accidental coin-avalanche)