One ethic that all can share is mutual respect (of a basic kind: taking one another into account as we live our separate lives together in this world). It boils down to a handful of absolutes: no killing, harming, coercing, stealing, or manipulating (which includes lying, cheating, etc.). That is way more than is in the Commandments.

A requirement of mutual respect follows from a belief in equality, which can be a sacral or a secular belief. It also follows from the observation that human beings have no choice but to effect choices, taking beliefs out of ethics altogether.

Mutual respect is readily applicable to the governance of society. A society governed by mutual respect would take us "Beyond Liberalism" (here in Medium, but not behind the paywall).