Is there a way a non-plumber can do something about the plume?

No. There's plenty you can do as plumber, though. Basically, the plume can
be usually be eliminated by using a long vertical flue section up to the
roof line. Even if that doesn't eliminate it, the plume will at least then
be in a location that isn't a nuisance.

Don't even think about trying to modify the flue outlet yourself. This could
result in death (and possibly manslaughter charges).

Christian.