Brackets are a convention, but not the most appropriate for every situation. I couldn't use brackets in my canonically bilingual comic. Why? There's language A, which is the tongue most commonly spoken throughout the story. More than 95% of the lines are in this language. Then there's language B, the less common one.
Normally, in such a situation, you put brackets around every line in language B. But I couldn't do that because... the effin' main character speaks that language! He does speak language A a little, but he's far from fluent.
Brackets say "this is the OTHER language." In my case, neither language is "the other one." Both are main languages, for different reasons.
I wound up using different fonts + different colors. Here's an episode that has lines in both languages. It's very long with multiple images, so it might take a while to fully load.
Another non-bracket example I've seen is actually putting the language/country symbols in every bubble. There is one comic that does it really well. I can't find it at the moment, but it worked.