Student or Learner
The noun bigamy originates in the Greek as a combination of the prefix bi-, meaning “double,” and gamos, which means “marrying.” There are some cultures and religions that promote, encourage and otherwise allow polygamy, but where it’s illegal, which is most of the Western Hemisphere, it’s called bigamy.
https://www.vocabulary.com/dictionary/bigamyDoes the underlined part in the given context mean that at least if not doing that, which is encouraging, they accept it, please? Honestly, I am confused with the meaning of otherwise since it has different meanings.
"...in any other way(s) allow polygamy, but..."
Please be aware that I'm neither a native English speaker nor a teacher.