There is a Netflix series called 野武士のグルメ and translated as Samurai Gourmet. I know there's an adaptation because many places outside Japan knows the Samurai word.
Is these words in Japanese interchangeable? Which is usual to use?
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侍 is a 武士 who has loyalty to a lord while 野武士 is one that doesn't have that relationship. So they are basically not interchangeable.
That said, it's not impossible to figuratively use 侍 to refer to those people. (武士 is called samurai in English, which looks a constant figurative use of the word from a Japanese point of view.)