Hello! So I am in Japan at the moment, and it hit me that I didn’t know how to say a polite, but not solemn goodbye, like you would say when leaving a shop or a restaurant. “Sayonara” feels too solemn, and “Matta ne” doesn’t make sense since I don’t plan on going back.
What would be the appropriate goodbye then ?
It’s mainly out of curiosity, “arigatou” or even plain english “thank you goodbye” seems to do the trick
If you’re leaving a restaurant it’s good to say ごちそうさまでした which is like “thanks for the meal!” and then you can do a good ありがとうございました
Leaving a shop, if you bought something you can say ありがとうございました or 世話様でした (おせわさまでした) [this means, thanks for taking care of me in a slightly formal yet casual store speech] at the counter. but if you don’t buy anything you don’t have to respond. Honestly Japanese people don’t even respond to the いらっしゃいませ when you come into a shop, so unless you buy something, you don’t really have to say anything.
In general, ありがとうございました is good. Just generally thanking them. Good broadly usable phrase.
For eating, ごちそうさまでした is a good option. They get very excited when foreigners say such things.
If you really want to get fancy, if it is near closing time you can say おつかれさまでした, which means “thank you for your hard work” and is what people say to each other when leaving work. Japanese people get really impressed if you say this one.