Is the 2024 BRZ only compatible with 98 octane fuel?

There aren't many gas stations that primarily offer 98 octane fuel.

Using 98 is better. Filling up with 98 costs around 500 as well.

Horizontally opposed engines are generally recommended to use 98 octane fuel. Porsche is the same. You can use 95, but it's better not to keep revving high consistently.