"Добрий вечір, друзі!"
Translation:Good evening, friends!
It has a comma because it’s a direct address. Direct addresses are always set off by commas in Ukrainian.
Surprised it didn't except "good night, friends" even though clicking on "вечір" gives "evening" and "night"
If you translate ‘good night’ when it’s a phrase referring to a good period of time, you can use either word. E.g. in ‘I had a good night at this place’ would be «Я гарно провів вечір/ніч в цьому місці» (the choice of the word will depend on how long you stayed there: if you stayed there past midnight, you can use ніч; otherwise, it’s вечір).
But ‘Good evening’ and ‘Good night’ are set expressions with special meaning. When we say ‘good evening’, we don’t mean that the evening is good, it’s just a way of saying ‘hi’. Similarly, ‘good night’ doesn’t mean the night is good, it’s a way of saying ‘bye’ or ‘sleep well’. So, you can’t translate them word-for-word, you need to use similar set expressions in Ukrainian.