Hey there! Well, my first effort would be to encourage total abandonment of the term "adultery" for Christians looking to police and punish each other. This is a legal term in OT law, and a capital crime. It should not be used in reference to spouses who are displeased with each other.

BTW- I take adultery to be a term for idolatrous practice, on the logic of a deity being a husband. I also believe accusing someone of adultery functions as a death threat and is inherently hateful.

What is the Bible's view of multiple spouses and concubines? That would seem to be clear. The heroes are wildly sexual. Christians are so addled by later traditions as to forget they made up their "vows" & ceremonies, or that it was done in the service of empire, and in open defiance of Jesus' teachings of non-attachment (cf. Mt 5:33).

With many Christians coerced into marriage--often when young-- with threats supplied by religious authorities—the question is one of theological fraud.

If a monogamous attachment is someone's goal perhaps it's laudable, but I'm unclear how the Bible can be used to manipulate another person into that situation. When Jacob married Rachel I'm unaware of him having to consult Leah on the matter. The Bible doesn't seem to provide many tools for punishing the sex lives of others. Even a divorce in OT law is done rather breezily and without a public forum for accusations and punishments.

In Colossians 3:9 we have "Do not lie to one another," which could function as an encouragement not to conceal non-monogamy. It should also enforce a safe space for disclosing uncomfortable truths, like sexual interest in others—though Christians have not wished to read the verse in such a light.

As usual, in thinking about sexual subjects, we're left with supposed "Christians" wanting what they want, and using God to get it—instead of doing the difficult work of being engaged to the reality of other people.