[thinkmassive]

You can sell goods and services locally and accept Bitcoin as payment. Craigslist even added a “cryptocurrency ok” flag you can set on your posts.

LocalBitcoins enables face to face transfers.

Bisq is a DEX that enables remote exchanges using any form of payment, including most centralized payment services, and even cash through snail mail.

[RestlessMind]

But then, the seller has to pay taxes - either business taxes if it is a merchant or capital gains taxes in case they sold an asset. And taxes are paid only in Fiat. So you still need Fiat integration somewhere.