https://wccftech.com/us-unlocked-samsung-galaxy-s9-and-s9-plus-get-fm-radio-support-via-latest-update/

FM radio was all the rage back in the day but now, with the widespread availability of streaming services, it has a niche audience. Make no mistake, a lot of people still listen to it, but most manufacturers deem it unnecessary and often don’t include it in their devices. People in remote areas that lack a stable data connection often rely on FM for their music needs. However, a person who has a Galaxy S9 and S9+ will very likely have access to high-speed internet, so the FM radio feels a bit unnecessary. Today, the carrier-unlocked variants of the 2018 Samsung flagships received FM radio functionality via an OTA update.

The unlocked Galaxy S9 and S9+ variants were initially supposed to have FM radio functionality right out of the box, but Samsung apparently ‘forgot’ to add the requisite APIs for it. Carrier-locked variants will have no such luck, though, despite being listed as supported devices by NextRadio. There are ways of getting FM Radio to work on the carrier-locked variants, but it involves flashing a new firmware and frankly isn’t worth the trouble.